John Gill Commentary Genesis 27:18

"And he came unto his father, and said, My father. And he said, Here am I. Who art thou, my son?" — Genesis 27:18 (ASV)

And he came to his father
Into the tent and apartment where he was: and said, my father ;
to try whether he was awake, and to let him know that he was come, since he could not see him: and he said, here [am] I ;
what do you have to say to me? who are you, my son ?
for, from the voice and the quick dispatch made, he suspected it was not his son Esau.