John Calvin Commentary Acts 7:23

"But when he was well-nigh forty years old, it came into his heart to visit his brethren the children of Israel." — Acts 7:23 (ASV)

When the time was fulfilled. Many infer from this that Moses was never estranged in mind from his nation; but the words of Stephen rather incline toward the contrary, namely, that the Spirit of God eventually awakened his mind, as it were, from sleep, so that he might eventually go visit his brothers, whom he had neglected for a long time.

It is to be supposed that he was not ignorant of the stock from which he came, since he had some sign of it in his flesh, and since the rumor about it was circulated in the court, because the king’s daughter could not adopt him as her son without some suspicion of wickedness, unless his origin had been known. Yet it was long before he had such courage that he dared reveal the love that he bore toward his own people.

And this serves in no small way to show forth the glory of God: that Moses, being ignorant of his calling, remains idle for a long time in the king’s court and is afterward called by the Lord, contrary to the expectation of all people, and his own as well. Therefore, this new care for his brothers which entered his mind came from a new and unusual prompting of God’s Spirit.