Charles Ellicott Commentary Exodus 34:27

"And Jehovah said unto Moses, Write thou these words: for after the tenor of these words I have made a covenant with thee and with Israel." — Exodus 34:27 (ASV)

Write thou these words. —Hebrew, Write for you these words, that is, put them in writing for your own use and the use of your people. This express command accounts for the assignment of so much space to what is mainly repetition. The requirement for this repetition can only be explained by the importance of the laws laid down under the circumstances of the Hebrew nation, and by the power of repetition to impress upon the conscience what is urged upon it by reiteration.

After the tenor of these words. — The summary of positive laws contained in this chapter (Exodus 34:12–26) was not intended to supersede the “Book of the Covenant,” but rather to confirm and reinforce it. The covenant was renewed not upon these words only, but “after the tenor,” that is, according to their general aspect or bearing.