This verse is made up of three conditions in which God will demand an accounting of the offender. The verse is complicated by the shifting from the second person your at the beginning of the verse to other persons with no clear transitions. Most translations will require considerable adjustment to make the meaning clear.

For your lifeblood: your is plural with reference to Noah and his family, and to their descendants in future generations. The expression is literally “the blood of your [plural] nefesh.” Although there is no verb in the construction, one is clearly understood, that is, “the taking of your life,” “the shedding of your blood, which takes away your life.” “Blood” represents the life force in human beings as well as in animals. In some translations this is expressed in the same way as in the previous verse: “… your blood, that is, your life.”

Require a reckoning translates a verb meaning to call someone to account, that is, to make someone responsible, or to make someone answer to a charge. New English Bible says “I will demand satisfaction.” The sense of the verse up to this point may be translated “If anyone takes another person’s life, I will demand an account” or “You will have to answer to me if you murder someone.” But as the rest of this verse and the next verse indicate, the meaning is that punishment, and not just an explanation, is what is required. So a number of translations say straight out “… I will punish him” or “I will pay him back for….” One translation says idiomatically “If any animal or person ends your life, I will make him [or, it] understand” (that is, “I will punish…”).

Of every beast I will require it means that punishment will be required for an animal that kills a person: the animal will be killed. See Exo 21.28-29. And of man is a shortened repetition of the previous clause and means that the person who kills another human being will be put to death; that is, the same law applies to the human murderer as to the animal that kills a person.

Of every man’s brother parallels the expression of every beast. Brother in this context means “a fellow human being,” “a neighbor,” “another person,” “anyone.” I will require the life of man expresses the same thought as above, concerning the punishment of the animal that kills a human. So here, if anyone takes another person’s life, murders him, God will require the murderer to pay with his life. Good News Translation has placed this thought at the beginning of verse 5: “If anyone takes human life, he will be punished.”

Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .