Gregory the Great
Catena Aurea · Johannesevangelium 8
Then said the Jews unto him, Now we know that thou hast a devil. Abraham is dead, and the prophets; and thou sayest, If a man keep my saying, he shall never taste of death. Art thou greater than our father Abraham, which is dead? and the prophets are dead; whom makest thou thyself? Jesus answered, If I honour myself, my honour is nothing; it is my Father that honoureth me; of whom ye say, that he is your God: Yet ye have not known him; but I know him: and if I should say, I know him not, I shall be a liar like unto you: but I know him, and keep his saying. Your father Abraham rejoiced to see my day: and he saw it, and was glad.
(Hom. xv. in Evang.) Abraham saw the day of the Lord even then, when he entertained the three Angels, a figure of the Trinity.