John Calvin Commentary Genesis 21:3

"And Abraham called the name of his son that was born unto him, whom Sarah bare to him, Isaac." — Genesis 21:3 (ASV)

And Abraham called the name. Moses does not mean that Abraham was the inventor of the name; but that he adhered to the name which had previously been given by the angel. This act of obedience, however, was worthy of commendation, since he not only ratified the word of God, but also executed his office as God’s minister. For, as a herald, he proclaimed to all, what the angel had committed to his trust.