Genesis 27:33

Isaac trembled exceedingly — Those that follow the choice of their own affections rather than the dictates of the Divine will, involve themselves in such perplexities as these. But he soon recovers himself, and ratifies the blessing he had given to Jacob, I have blessed him, and he shall be blessed — He might have recalled it, but now at last he is sensible he was in an error when he designed it for Esau. Either recollecting the Divine oracle, or having found himself more than ordinarily filled with the Holy Ghost when he gave the blessing to Jacob, he perceived that God did as it were say Amen to it.