the cause
Exodus 21:20
And if a man smite his servant, or his maid, with a rod, and he die under his hand; he shall be surely punished.
Exodus 21:21
Notwithstanding, if he continue a day or two, he shall not be punished: for he is his money.
Exodus 21:26
And if a man smite the eye of his servant, or the eye of his maid, that it perish; he shall let him go free for his eye's sake.
Exodus 21:27
And if he smite out his manservant's tooth, or his maidservant's tooth; he shall let him go free for his tooth's sake.
Leviticus 25:43
Thou shalt not rule over him with rigour; but shalt fear thy God.
Leviticus 25:46
And ye shall take them as an inheritance for your children after you, to inherit them for a possession; they shall be your bondmen for ever: but over your brethren the children of Israel, ye shall not rule one over another with rigour.
Deuteronomy 15:12-15
12
And if thy brother, an Hebrew man, or an Hebrew woman, be sold unto thee, and serve thee six years; then in the seventh year thou shalt let him go free from thee.
13
And when thou sendest him out free from thee, thou shalt not let him go away empty:
14
Thou shalt furnish him liberally out of thy flock, and out of thy floor, and out of thy winepress: of that wherewith the LORD thy God hath blessed thee thou shalt give unto him.
15
And thou shalt remember that thou wast a bondman in the land of Egypt, and the LORD thy God redeemed thee: therefore I command thee this thing to day.
Jeremiah 34:14-17
14
At the end of seven years let ye go every man his brother an Hebrew, which hath been sold unto thee; and when he hath served thee six years, thou shalt let him go free from thee: but your fathers hearkened not unto me, neither inclined their ear.
15
And ye were now turned, and had done right in my sight, in proclaiming liberty every man to his neighbour; and ye had made a covenant before me in the house which is called by my name:
16
But ye turned and polluted my name, and caused every man his servant, and every man his handmaid, whom ye had set at liberty at their pleasure, to return, and brought them into subjection, to be unto you for servants and for handmaids.
17
Therefore thus saith the LORD; Ye have not hearkened unto me, in proclaiming liberty, every one to his brother, and every man to his neighbour: behold, I proclaim a liberty for you, saith the LORD, to the sword, to the pestilence, and to the famine; and I will make you to be removed into all the kingdoms of the earth.
Ephesians 6:9
And, ye masters, do the same things unto them, forbearing threatening: knowing that your Master also is in heaven; neither is there respect of persons with him.
Colossians 4:1
Masters, give unto your servants that which is just and equal; knowing that ye also have a Master in heaven.