John Gill Commentary Genesis 27:20

"And Isaac said unto his son, How is it that thou hast found it so quickly, my son? And he said, Because Jehovah thy God sent me good speed." — Genesis 27:20 (ASV)

And Isaac said to his son Supposing him to be Esau: how [is it] that you have found [it] so quickly, my son?

that is, the venison; that he had met with it so soon in the field, and got it dressed and ready in so short a time, which was not common, and seemed to be too little for doing all this in it, and so still created some suspicion of deceit:

and he said, because the Lord your God brought [it] to me; which was another falsehood; for it was not the Lord, but his mother brought it to him: and this seems to be the most marvellous of all, that so good a man should dare to bring the name of the Lord God into this affair; indeed he does not say the Lord my God, or our God, but your God; which some think was done on purpose, the more to cover the deceit, because they suppose that Esau, whom Jacob impersonated, was an idolater, but this is not so evident; rather it looks as if Jacob had not the confidence to call the Lord his God with a lie in his mouth.