You shall fear the LORD your God; you shall serve Him, and to Him you shall hold fast, and take oaths in His name.
Deuteronomy 10:20
Surrounding context
10:19 Therefore love the stranger, for you were strangers in the land of Egypt.
10:20 You shall fear the LORD your God; you shall serve Him, and to Him you shall hold fast, and take oaths in His name.
10:21 He is your praise, and He is your God, who has done for you these great and awesome things which your eyes have seen.