A.T. Robertson Commentary Acts 7:21

"and when he was cast out, Pharaoh`s daughter took him up, and nourished him for her own son." — Acts 7:21 (ASV)

When he was cast out (εκτεθεντος αυτου). Genitive absolute with first aorist passive participle of εκτιθημ.

Took up (ανειλατο). Second aorist middle indicative (with first aorist vowel α instead of ε as often in the Koine) of αναιρεω, common in the N.T. in the sense of take up and make away with, to kill as in verse 28, but here only in the N.T. in the original sense of taking up from the ground and with the middle voice (for oneself). Quoted here from Ex 2:5. The word was used of old for picking up exposed children as here. Vincent quotes Aristophanes (Clouds, 531): "I exposed (the child), and some other women, having taken it, adopted (ανειλετο) it." Vulgate has sustulit. "Adopted" is the idea here. "After the birth of a child the father took it up to his bosom, if he meant to rear it; otherwise it was doomed to perish" (Hackett).

Nourished him for her own son (ανεθρεψατο αυτον εαυτη εις υιον). Literally, "she nursed him up for herself (εαυτη besides middle voice) as a son." This use of εις=as occurs in the old Greek, but is very common in the LXX as a translation of the Hebrew le. The tradition is that she designed Moses for the throne as the Pharaoh had no son (Josephus, Ant. ii. 9, 7).