As for Ishmael, …: this switches God’s line of thought to Ishmael. In some languages this may be translated “I will speak now about Ishmael,” or “This is what I have to say about Ishmael,” or “I have heard what you asked me to do for Ishmael.” I have heard is probably also a play on the name of Ishmael, which parallels the play on the name of Isaac in the previous verses. See 16.11.

For behold see 1.31.

I will bless him introduces the promise of fertility and a line of descendants for Ishmael. See the same for Sarah in verse 16. Since this promise of blessing follows the promise of blessing on Isaac, some translations say “I will bless him too.” For make him fruitful and multiply him as a metaphor indicating fertility, see 1.22 and verses 2 and 6.

He shall be the father of twelve princes: the names of the sons of Ishmael and the twelve Ishmaelite tribes are listed in 25.12-18. The word translated princes is literally “ones elevated or lifted up.” The term can refer to chiefs, rulers, nobles. If the expression He shall be the father of is not suitable, we may also say, for example, “He will have twelve sons who will be chiefs.”

And I will make him a great nation: the same was said of Abraham in 12.2. See there for discussion.

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 .