Exodus 23:20-22

Behold, I send an angel before thee, to keep thee by the way, and to bring thee into the place which I have prepared. Take ye heed before him, and hearken unto his voice; provoke him not; for he will not pardon your transgression: for my name is in him. But if thou shalt indeed hearken unto his voice, and do all that I speak; then I will be an enemy unto thine enemies, and an adversary unto thine adversaries.