John Gill Commentary Luke 4:8

"And Jesus answered and said unto him, It is written, Thou shalt worship the Lord thy God, and him only shalt thou serve." — Luke 4:8 (ASV)

Jesus answered and said to him
The following words, with indignation at him, and detestation of his proposals:

get you behind me, Satan ;
which are omitted in the Vulgate Latin, Syriac, Persic, and Ethiopic versions, and in three ancient copies of Beza's, and in his most ancient one; but stand in other copies, and in the Arabic version.

For it is written, you shall worship the Lord your God, and him only
you shall serve .
This passage stands in (Deuteronomy 6:13) where the words are, "you shall fear the Lord your God, and serve him, and you shall swear by his name": the last clause is not cited by Christ at all, swearing being only a species, or part of religious worship; and the other two clauses are somewhat different from the original text, as here cited, and may be accounted for:

instead of "fear the Lord", it is "worship the Lord"; and the one well explains the other; the fear of God being often, in Scripture, put for the whole worship of God, both internal and external: and in the next clause, the word "only" is added by Christ, as expressing the true sense of it, and agreeably to other places of Scripture, particularly (1 Samuel 7:3) , (See Gill on Matthew 4:10).