Q: What is forbidden in the sixth commandment?
A: The sixth commandment forbiddeth the taking away of our own life, or the life of our neighbour unjustly, or whatsoever tendeth thereunto.

Acts 16:28. But Paul cried with a loud voice, saying, Do thyself no harm: for we are all here.
Genesis 9:6. Whoso sheddeth man's blood, by man shall his blood be shed: for in the image of God made he man.
Matthew 5:22. But I say unto you, That whosoever is angry with his brother without a cause shall be in danger of the judgment: and whosoever shall say to his brother, Raca, shall be in danger of the council: but whosoever shall say, Thou fool, shall be in danger of hell fire. 
John 3:15. Whosoever hateth his brother is a murderer: and ye know that no murderer hath eternal life abiding in him.
Galatians 5:15. But if ye bite and devour one another, take heed that ye be not consumed one of another.
Proverbs 24:11-12. If thou forbear to deliver them that are drawn unto death, and those that are ready to be slain; If thou sayest, Behold, we knew it not; doth not he that pondereth the heart consider it? and he that keepeth thy soul, doth not he know it? and shall not he render to every man according to his works?
Exodus 21:18-32. And if men strive together, and one smite another with a stone, or with his fist, and he die not, but keepeth his bed: If he rise again, and walk abroad upon his staff, then shall he that smote him be quit: only he shall pay for the loss of his time, and shall cause him to be thoroughly healed. And if a man smite his servant, or his maid, with a rod, and he die under his hand; he shall be surely punished. Notwithstanding, if he continue a day or two, he shall not be punished: for he is his money. If men strive, and hurt a woman with child, so that her fruit depart from her, and yet no mischief follow: he shall be surely punished, according as the woman's husband will lay upon him; and he shall pay as the judges determine. And if any mischief follow, then thou shalt give life for life, eye for eye, tooth for tooth, hand for hand, foot for foot, burning for burning, wound for wound, stripe for stripe. 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. 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. If an ox gore a man or a woman, that they die: then the ox shall be surely stoned, and his flesh shall not be eaten; but the owner of the ox shall be quit. But if the ox were wont to push with his horn in time past, and it hath been testified to his owner, and he hath not kept him in, but that he hath killed a man or a woman; the ox shall be stoned, and his owner also shall be put to death. If there be laid on him a sum of money, then he shall give for the ransom of his life whatsoever is laid upon him. Whether he have gored a son, or have gored a daughter, according to this judgment shall it be done unto him. If the ox shall push a manservant or a maidservant; he shall give unto their master thirty shekels of silver, and the ox shall be stoned.