The first three chapters of Deuteronomy were basically a history lesson, reminding the people of what they had been through up to that point. By the time we get to chapter four, the history lesson shifts more into a sermonic mode. The recounting of events wasn’t just for history buffs; instead, it served a purpose, showing them the power and grace of God working among the people, and that even though they messed up, the Lord was still going to honor His covenant with them.
Chapter four begins with the Hebrew word (a conjunction and an adverb), we‘attah, which can be translated as “And now” or “So now.” They just had reviewed their recent history, a reminder of what God had done in bringing them to this point — thus, or “so now,” they are to do what God tells them to do (see also Deut. 10:12) in response.