Deuteronomy 10:20 in the King James Version
Thou shalt fear the LORD thy God; him shalt thou serve, and to him shalt thou cleave, and swear by his name.
Context
19 Therefore love the foreigner, for you were foreigners in the land of Egypt.
20 You shall fear the LORD your God. You shall serve him. You shall cling to him, and you shall swear by his name.
21 He is your praise, and he is your God, who has done for you these great and awesome things which your eyes have seen.