מדרש על בראשית 16:11

Abraham, modest and unassuming as he was, was ready to do justice to Sarah, and he conferred full power upon her to dispose of Hagar according to her pleasure. He added but one caution, "Having once made her a mistress, we cannot again reduce her to the state of a bondwoman." Unmindful of this warning, Sarah exacted the services of a slave from Hagar. Not alone this, she tormented her, and finally she cast an evil eye upon her, so that the unborn child dropped from her, and she ran away. On her flight she was met by several angels, and they bade her return, at the same time making known to her that she would bear a son who should be called Ishmael--one of the six men who have been given a name by God before their birth, the others being Isaac, Moses, Solomon, Josiah, and the Messiah.

Balaam said: Of the seventy nations that the Holy One, blessed be He, created in His world, He did not put His name on any one of them except on Israel; and since the Holy One, blessed be He, made the name of Ishmael similar to the name of Israel, woe to him who shall live in his days, as it is said, "Alas, who shall live when God establisheth him?" (Num. 24:23).

Whence do we know about Ishmael? Because it is said, "And the angel of the Lord said unto her, Behold, thou art with child,… and thou shalt call his name Ishmael" (Gen. 16:11). Why was his name || called Ishmael? Because in the future the Holy One, blessed be He, will hearken to the cry of the people arising from (the oppression) which the children of Ishmael will bring about in the land in the last (days); therefore was his name called Ishmael.