John Gill Commentary Acts 7:25

"and he supposed that his brethren understood that God by his hand was giving them deliverance; but they understood not." — Acts 7:25 (ASV)

For he supposed his brethren would have understood him ,
&c.] From his being an Hebrew in such high life; from his wonderful birth, and miraculous preservation in his infancy, and education in Pharaoh's court; and from the promise of God that he would visit them and save them:

how that God by his hand would deliver them :
wherefore he was the more emboldened to kill the Egyptian, believing that his brethren would make no advantage of it against him; but look upon it as a beginning and pledge of their deliverance by him:

but they understood not ;
or "him not", as the Ethiopic version reads; they did not understand that he was to be their deliverer, or that this action of his was a token of it.