Genesis 17:20 is the Lord's answer to the previous verse's quiet sadness. Targum Pseudo-Jonathan renders it with full warmth. Concerning Ishmael I have heard thy prayer. Behold, I have blessed him; and I will spread him abroad, and multiply him very greatly. Twelve princes shall he beget, and I will give him to be a great people.
The verb heard is doing beautiful work. Ishmael's own name means God hears (Genesis 16:11). Now, a chapter later, Abraham prays for Ishmael, and the Lord says, in effect, I have heard your prayer too — and the name I gave him through his mother is also the promise I keep to you.
Twelve princes. A great nation. A people spread wide. This is not a consolation prize. This is its own covenant of flourishing, and the Targum refuses to downplay it. Ishmael is blessed, multiplied, established, and named a father of nations. The covenant of Torah will go through Isaac, but the blessing of life goes to Ishmael no less generously.
The Maggid hears one of the most mature parenting moments in Genesis. Abraham does not stop loving the son he has just because a son has been promised. And the Lord, rather than rebuking Abraham for the divided heart, blesses both children. Your prayer was heard for Ishmael, He says (Genesis 17:20). Your faithfulness will be rewarded through Isaac. Two promises at once, to one father, on the same day.