Genesis 25:24

24.And when her days to be delivered were fulfilled. Moses shows that the intestine strife in her womb continued to the time of bringing forth; for it was not by mere accident that Jacob seized his brother by the heel and attempted to get out before him. The Lord testified by this sign that the effect of his election does not immediately appear; but rather that the intervening path was strewed with troubles and conflicts. Therefore Esau’s name was allotted to him on account of his asperity; which even from earliest infancy assumed a manly form; but the name Jacob signifies that this giant, vainly striving in his boasted strength, had still been vanquished. (32)