## after they came out from the land of Egypt ##

Here the word "they" refers to the people of Israel.

## at its fixed time of year ##

AT: "at the time of each year that I have determined"

## follow all the regulations, and obey all the decrees​ ##

These two phrases mean basically the same thing and are combined for emphasis. (See: [[rc://en/ta/man/translate/figs-parallelism]])