Commentary for Genesis 27:20

ויאמר יצחק, because of the sound of Yaakov’s voice his mind had been alerted so that he began to examine the person standing before him more closely. The fact that so little time had elapsed since he instructed Esau to go hunting made him suspicious that it might not be Esau standing there.

How is it that you found it so quickly. Yitzchok had intentionally given Eisov an arduous assignment to increase his merit. Hashem … brought it about for me. I myself did not expect to find the prey so close by. Your God. This was a sign the animal was sent for this purpose in your merit.

כי הקרה ה' אלוקיך לפני, “because the Lord your G–d has so arranged it for my benefit on this day.” Esau used the same phraseology that Eliezer had used when on his way to find a wife for Yitzchok (Genesis 24,12) The ram which was entangled by its horns in Genesis 22,3 was also something that G–d had made happen just for that occasion, so that Avraham would not feel that he had come all the way without G–d accepting an offering from him. The root קרה occurs only in connection with things which occurred without visible preparation for use at a certain moment. (B’reshit Rabbah, 65,19) According to the Midrash there, the moment the person before him used the tetragram when referring to G–d, Yitzchok knew that that person could not be Esau.

כי הקרה ה' אלוקיך, “your merit has assisted me to accomplish my mission so quickly, seeing that what I did was for your sake.”