No, for I have chosen him: Revised Standard Version has supplied No as the LORD’s response to his own question in verse 17a; that is, the LORD will not hide from Abraham his intention to destroy Sodom. Good News Translation‘s negative statement in verse 17 substitutes for the negative response here. If a positive statement has been used in verse 17, then No will not be appropriate here. What follows is the reason for not hiding his intentions from Abraham. Chosen is literally “known”; see Revised Standard Version footnote. The verb “know” in Hebrew has a very wide range of meanings, and its usage must be determined largely by context. It is used here as in Amos 3.2; Hos 13.5.
That he may charge his children and his household after him: this is a clause of purpose often introduced in English with “in order that” or “so that.” Charge his children means to “command,” “order,” “direct,” “instruct” his children. And his household after him is another way of referring to Abraham’s descendants, that is, “and all his descendants.”
Abraham’s commands or instructions to his descendants are to keep the way of the LORD, which means to do as the LORD requires, to live as God wants them to live or, as Good News Translation says, “to obey me.” Biblia Dios Habla Hoy says “Obey my teachings.” This is then further defined as by doing righteousness and justice. For discussion of righteousness see 15.6. Justice is derived from the verb “to judge [a case]” as used in 16.5, for instance, where an angry Sarai asks the LORD to judge between her and Abram to decide who is at fault. The noun translated justice meant in the first place the decision of a judge in a legal case; but since legal judgments often became precedents, the term came to have the sense of what was in accord with right behavior and right living as it had been established, or in the sense of dealing with other people in the right manner. So to “do justice” means to act in accord with what is right, or to treat one’s fellow human being in a right manner. Both righteousness and justice refer to doing what God requires, living in a good and just manner, doing what is right and correct. We may also say, for example, “to do what is right and acceptable to the LORD.”
Abraham is required to command, teach his children and household. This is the condition necessary for the LORD to carry out the promises made to him: so that the LORD may bring to Abraham what he has promised him. Since the LORD is the speaker, we may say here, for example, “and then I will…” or “in order that I may….” He has promised may also be shifted to “what I have promised Abraham” or “so that I may do for him what I have promised him.”
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 .