Deuteronomy 6:13-15

Thou shalt fear Jehovah thy God; and him shalt thou serve, and shalt swear by his name. Ye shall not go after other gods, of the gods of the peoples that are round about you; for Jehovah thy God in the midst of thee is a jealous God; lest the anger of Jehovah thy God be kindled against thee, and he destroy thee from off the face of the earth.