Genesis 32:26

Let me go — The angel, by an admirable condescension, speaks Jacob fair to let him go, as God said to Moses, Exodus 32:10. Let me alone. Could not a mighty angel get clear of Jacob's grapples? He could; but thus he would put an honour upon Jacob's faith and prayer. The reason the angel gives why he would be gone is because the day breaks, and therefore he would not any longer detain Jacob, who had business to do, a journey to go, a family to look after. And he said, I will not let thee go except thou bless me — He resolves he will have a blessing, and rather shall all his bones be put out of joint, than he will go away without one. Those that would have the blessing of Christ must be in good earnest, and be importunate for it.