Exodus 23:20-22

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