And the Angel of the Lord called unto him out of heaven
Not a created angel, but the eternal one, the Son of God, who perhaps appeared in an human form, and spoke with an articulate voice, as be frequently did; for that this was a divine Person is clear from his swearing by himself, and renewing the promise unto Abraham, ( Genesis 22:16-18 ) :
and said, Abraham, Abraham;
the repeating his name denotes haste to prevent the slaughter of his son, which was just upon the point of doing, and in which Abraham was not dilatory, but ready to make quick dispatch; and therefore with the greater eagerness and vehemency the angel calls him by name, and doubles it, to raise a quick and immediate attention to him, which it did:
and he said, here [am] I:
ready to hearken to what shall be said, and to obey what should be ordered, (See Gill on Genesis 22:1).