John Gill 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)

And the Lord said unto Moses
Being still with him on the mount:

write you these words ;
expressed in the preceding verses, from (Exodus 34:11–27) , as he before had written in a book all those laws, contained in (Exodus 21:1–23:33) called the book of the covenant, (Exodus 24:4Exodus 24:7) and which perhaps might be destroyed, as well as the two tables were broken; and therefore upon the renewal of the covenant here, there is a repetition made of the principal laws before given, which are ordered also to be written in a book, which may very well be called by the same name, since it follows:

for after the tenor of these words I have made a covenant with
you and with Israel ,
with Moses, as their representative and mediator, and with them represented by him: what is above related carries in it the form of a covenant between them, God having declared on his part what he would do for them, and what laws and rules he required to be observed on their part; which Moses assented to in their name, and was ordered to write them down, that he might repeat them to them.