You shall fear the LORD your God. You shall serve him and hold fast to him, and by his name you shall swear.
Leviticus 19:12. And ye shall not swear by my name falsely. Although Moses is treating of the duties of the Second Table, and had previously forbidden men to deal fraudulently with their neighbors, he still adds this sentence by way of confirmation.
Here is a most pathetic exhortation to obedience, inferred from the premises, and urged with very powerful arguments and a great deal of persuasive rhetoric. Moses brings it in like an orator, with an appeal to his auditors And now, Israel, what doth the Lord thy God require of thee? Deu 10:12. Ask what he requires; as David (Psa 116:12), What shall I render?
Commenting on Deuteronomy 10:12-22
Thou shalt fear the Lord thy God,.... Which includes the whole worship of him, external and internal: him shalt thou serve; heartily and sincerely, according to his revealed will, and him only: and to him shall thou cleave; and not turn aside to follow other gods, and worship them: and swear by his name; and his only, whenever it is necessary to take an oath...