Dharmic religions - Hinduism, Buddhism, Sikhism, and Jainism - espouse a belief in Karma.
Karma, in Sanskrit, means "works" or "actions". In Dharmic religions, it is the notion that your actions will influence your future - which is common sense - but it's applied in a devious way when combined with the doctrine of reincarnation in order to form a truly monstrous teaching.
Nearly everyone has observed situations in which someone appears to be suffering, despite not having done anything particularly wrong to deserve it:
Ecclesiastes 8:14
14 There is a vanity which is done upon the earth; that there be just men, unto whom it happeneth according to the work of the wicked; again, there be wicked men, to whom it happeneth according to the work of the righteous: I said that this also is vanity.
The origins of the beliefs in both Karma and reincarnation - the two doctrines are inextricably linked in these religions - are attempts to make sense of this dilemma, and suffering in general, without divine revelation.
The reasoning behind belief in Karma is easy to follow:
This line of reasoning leads to scriptures which say the following:
Chandogya Upanishad - Book 5, Chapter 10
7 Among them, those who did good work in this world attain a good birth accordingly. They are born as a brāhmin, a kṣatriya, or a vaiśya. But those who did bad work in this world attain a bad birth accordingly, being born as a dog, a pig, or as a casteless person.
Brihadaranyaka Upanishad - Book 4, Chapter 4
When body grows weak through age or disease, the Self separates itself from the limbs, as a mango, a fig, a banyan fruit separates itself from the stalk; man hastens back to birth, goes, as before, from birth to birth.
As a caterpillar, having reached the end of a blade of grass, takes hold of another blade, then draws its body from the first, so the Self having reached the end of his body, takes hold of another body, then draws itself from the first.
This Self is Spirit. He is knowledge, mind, life, sight, hearing, earth, water, wind, air, light, darkness, desire, absence of desire, anger, placability, right, wrong; He is everything; He is this and that. Whatever his conduct and character in one life, he has it in his next; if good in one, he is good in another; if a sinner in one, he is a sinner in another; his good karma makes him good, his sinful karma makes him sinful.
Hence they say that soul is full of desire. He wills according to his desire; he acts according to his will; he reaps what he sows. Here is my authority: "Self goes where man's mind goes. Whatever his actions in this world, he enjoys their reward in the next; that over, he returns for action's sake. I speak of a man with desire; but what is he who has no desire? He has no desire, because he has attained his desire; desire of Self is no desire. He does not die like others; he is of Spirit, he becomes Spirit."
Garuda Purana - Chapter 5
1 Garuḍa said: Tell me, O Keśava (Vishnu), by what sins particular signs are produced, and to what sorts of birth such sins lead?
2 The Blessed Lord said: The sins on account of which the sinful returning from hell come to particular births, and the signs produced by particular sins - these hear from me.
3 The murderer of a Brāhmaṇ becomes consumptive, the killer of a cow becomes hump-backed and imbecile, the murderer of a virgin becomes leprous - all three born as outcastes.
4 The slayer of a woman and the destroyer of embryos becomes a savage full of diseases; who commits illicit intercourse, a eunuch; who goes with his teacher's wife, diseased-skinned.
5 The eater of flesh becomes very red; the drinker of intoxicants, one with discoloured teeth; the Brāhmaṇ who, on account of greed, eats what should not be eaten, becomes big-bellied.
6 He who eats sweet foods, without giving to others, becomes swollen-necked; who gives impure food at a Śrāddha ceremony is born a spotted leper.
7 The man who, through pride, insults his teacher, becomes an epileptic; who despises the Vedas and the Śāstras certainly becomes jaundiced.
8 Who bears false witness becomes dumb; who breaks the meal-row becomes one-eyed; who interferes with marriage becomes lipless; who steals a book - is born blind.
9 Who strikes a cow or a Brāhmaṇ with his foot is born lame and deformed; who speaks lies becomes a stammerer, and who listens to them becomes deaf.
10 A poisoner becomes insane; an incendiary becomes bald; who sells flesh becomes unlucky; who eats fled of other beings becomes diseased.
11 Who steals jewels is born in a low caste; who steals gold gets diseased nails; who steals any metal becomes poverty-stricken.
Bhagavad Gita 6:40-42
40 Lord Shri Krishna replied: My beloved child! There is no destruction for him, either in this world or in the next. No evil fate awaits him who treads the path of righteousness.
41 Having reached the worlds where the righteous dwell, and having remained there for many years, he who has slipped from the path of spirituality will be born again in the family of the pure, benevolent and prosperous.
42 Or, he may be born in the family of the wise sages, though a birth like this is, indeed, very difficult to obtain.
Manusmriti - Chapter 11
48 Some wicked men suffer a change of their (natural) appearance in consequence of crimes committed in this life, and some in consequence of those committed in a former (existence).
49 He who steals the gold (of a Brahmana) has diseased nails; a drinker of (the spirituous liquor called) Sura, black teeth; the slayer of a Brahmana, consumption; the violator of a Guru’s bed, a diseased skin;
50 An informer, a foul-smelling nose; a calumniator, a stinking breath; a stealer of grain, deficiency in limbs; he who adulterates (grain), redundant limbs;
51 A stealer of (cooked) food, dyspepsia; a stealer of the words (of the Veda), dumbness; a stealer of clothes, white leprosy; a horse-stealer, lameness. The stealer of a lamp will become blind; he who extinguishes it will become one-eyed; injury (to sentient beings) is punished by general sickliness; an adulterer (will have) swellings (in his limbs).
52 Thus in consequence of a remnant of (the guilt of former) crimes, are born idiots, dumb, blind, deaf, and deformed men, who are (all) despised by the virtuous.
53 Penances, therefore, must always be performed for the sake of purification, because those whose sins have not been expiated, are born (again) with disgraceful marks.
Manusmriti - Chapter 12
9 Through sinful acts due to the body, man becomes inanimate; through those of speech, a bird or a beast; and through those of mind, he is born in the lowest caste.
Digha Nikaya - Sangiti Sutta 3:2
2 Nine unfortunate, inopportune times for leading the holy life: A Tathagata has been born in the world, Arahant, fully-enlightened Buddha, and the Dharnma is taught which leads to calm and perfect Nibbana, which leads to enlightenment as taught by the Well-Farer, and this person is born in a hell-state (nirayam), among the animals, among the petas (hungry ghosts), among the asuras (demons), in a long-lived group of deva (gods), or he is born in the border regions among foolish barbarians where there is no access for monks and nuns, or male and female lay-followers, or he is born in the Middle Country, but he has wrong views and distorted vision, thinking:
"There is no giving, offering or sacrificing, there is no fruit or result of good or bad deeds; there is not this world and the next world; there are no parents and there is no spontaneous rebirth; there are no ascetics and Brahmins in the world who, having attained to the highest and realised for themselves the highest knowledge about this world and the next, proclaim it"; or he is born in the Middle Country but lacks wisdom and is stupid, or is deaf and dumb and cannot tell whether something has been well said or ill said; or else no Tathagata has arisen, and this person is born in the Middle Country and is intelligent, not stupid, and not deaf or dumb, and well able to tell whether something has been well said or ill said.
Majjhima Nikaya - Balapandita Sutta 25
25 "If, sometime or other, at the end of a long period, that fool comes back to the human state, it is into a low family that he is reborn - into a family of outcasts or hunters or bamboo-workers or cartwrights or scavengers - one that is poor with little to eat and drink, surviving with difficulty, where he scarcely finds food and clothing; and he is ugly, unsightly, and misshapen, sickly, blind, cripple-handed, lame, or paralysed; he gets no food, drink, clothes, vehicles, garlands, scents and unguents, bed, lodging, and light; he misconducts himself in body, speech, and mind, and having done that, on the dissolution of the body, after death, he reappears in a state of deprivation, in an unhappy destination, in perdition, even in hell.
Majjhima Nikaya - Culakammavibhanga Sutta 7-8
7 "Here, student, some man or woman is given to injuring beings with the hand, with a clod, with a stick, or with a knife. Because of performing and undertaking such action, on the dissolution of the body, after death, he reappears in a state of deprivation. But if instead he comes back to the human state, then wherever he is reborn he is sickly. This is the way, student, that leads to sickliness, namely, one is given to injuring beings with the hand, with a clod, with a stick, or with a knife.
8 "But here, student, some man or woman is not given to injuring beings with the hand, with a clod, with a stick, or with a knife. Because of performing and undertaking such action, on the dissolution of the body, after death, he reappears in a happy destination. But if instead he comes back to the human state, then wherever he is reborn he is healthy. This is the way, student, that leads to health, namely, one is not given to injuring beings with the hand, with a clod, with a stick, or with a knife.
As can be seen above, our past lives, according to these religions, directly affect our circumstances in future lives. Therefore, because everyone is reaping the fruit of what they have done in a past life, the child born with a horrendous birth defect is not truly to be pitied. The person born in squalor, or to poor parents, or has some incurable illness, is likewise being punished for something that they did in a past life. It's only those born to a high Caste, those in power, or those who otherwise prosper, that are being rewarded for their virtue in a previous life.
Therefore, no matter one's lot in life, they assure them that they are being punished/rewarded for past lifetimes lived that they (conveniently) have absolutely no recollection of ever having experienced.
Observe that:
This doctrine is the root and heart of the Caste System in India. Even though the Caste System is officially illegal in India today, it still affects the lives of millions of Indians, because it's enforced culturally, just as it has been for many hundreds of years - a rigid stratification of society, based on belief in reincarnation, and justified by the false doctrine of Karma.
To begin, it makes sense to address passages in the Bible which would appear, on their surface, to agree with the doctrine of Karma. For instance:
Galatians 6:7
7 Be not deceived; God is not mocked: for whatsoever a man soweth, that shall he also reap.
There are many verses which teach something similar to the above (Hosea 8:7, Proverbs 11:18, 22:8: 2 Corinthians 9:6). However, it would be a grave error to conflate the message of this verse with the doctrine of Karma.
The Word of God teaches "Whatsoever a man soweth, that shall he also reap". The doctrine of Karma teaches "Whatsoever a man soweth, that shall he also reap, but and if he doesn't, his sin will be brought to bear on him in a future life". As mentioned in the introduction, it's when reincarnation is involved that this doctrine becomes so unimaginably cruel and evil.
Although the principal of sowing and reaping is Biblical, it is not an explanation for all suffering that a person will undergo in their lives. The following passage is exemplary of this fact:
John 9:1-3
1 And as Jesus passed by, he saw a man which was blind from his birth.
2 And his disciples asked him, saying, Master, who did sin, this man, or his parents, that he was born blind?
3 Jesus answered, Neither hath this man sinned, nor his parents: but that the works of God should be made manifest in him.
Above, the misconception that the disciples had was that since the blind man was suffering, either he, or his parents, did something bad to deserve it. And, in response, the Lord directly refutes that misconception.
Not all suffering is retribution for sin. Some, to be sure, is (Proverbs 13:15), especially if you are a Christian (Hebrews 12:6). However, the idea that children born with birth defects, or otherwise difficult and painful conditions, are somehow to blame for their misery, is the height of demonic cruelty, slander, and injustice.
The book of Job is perhaps the best place to examine Karma in light of the Bible, because its main theme is an examination of a righteous man suffering for something that he did nothing in particular to deserve (Job 2:3).
In it, Job's friends, as evidenced by dozens of their statements, believed that Karma would come to bear with certainty on all evildoers. Therefore, they reasoned that the only explanation for Job's suffering must have been his sin:
Job 4:1, 7-8
1 Then Eliphaz the Temanite answered and said,
...
7 Remember, I pray thee, who ever perished, being innocent? or where were the righteous cut off?
8 Even as I have seen, they that plow iniquity, and sow wickedness, reap the same.
Job 8:1-6
1 Then answered Bildad the Shuhite, and said,
2 How long wilt thou speak these things? and how long shall the words of thy mouth be like a strong wind?
3 Doth God pervert judgment? or doth the Almighty pervert justice?
4 If thy children have sinned against him, and he have cast them away for their transgression;
5 If thou wouldest seek unto God betimes, and make thy supplication to the Almighty;
6 If thou wert pure and upright; surely now he would awake for thee, and make the habitation of thy righteousness prosperous.
Notice their tone. They insinuate that if Job was innocent, God would be unjust to let him suffer this way, and surely if he were righteous, God would have helped him by now, otherwise God's righteousness is called into question. This is the same faulty reasoning that underpins a belief in Karma.
Later in the book, Job states that had the tables been turned, he wouldn't have reasoned the way that his friends did, and would instead comfort them despite their misery:
Job 16:1-5
1 Then Job answered and said,
2 I have heard many such things: miserable comforters are ye all.
3 Shall vain words have an end? or what emboldeneth thee that thou answerest?
4 I also could speak as ye do: if your soul were in my soul's stead, I could heap up words against you, and shake mine head at you.
5 But I would strengthen you with my mouth, and the moving of my lips should asswage your grief.
Job said that he would comfort them, because what he was going through was proof that people suffer who haven't done anything particularly wrong to deserve it, and often people suffer wildly disproportionately in relation to the sins that they commit.
Towards the end of the book of Job, God makes an appearance, and rebukes Job's friends:
Job 42:7
7 And it was so, that after the Lord had spoken these words unto Job, the Lord said to Eliphaz the Temanite, My wrath is kindled against thee, and against thy two friends: for ye have not spoken of me the thing that is right, as my servant Job hath.
If there's one lesson that can be gleaned from the book of Job, it's that the causes of suffering are often mysterious, and only God knows the exact, precise reason that an individual suffers.
You, as a human being, most often have no idea for certain why so-and-so is going through whatever they are going through. Speculating that those suffering are doing so because of their own sins in a past life, then, may lead you to place blame squarely on an innocent person.
Karma, in light of the Bible, is an evil false doctrine. It was invented by wicked men trying to understand the world, while rejecting divine revelation.