Along with the focus on relationships and heart issues, Deuteronomy 4 includes several injunctions to not make any images or worship other gods. While this might seem irrelevant to many today who do not experience temptations of idolatry in a physical sense, Moses was speaking to a people who had struggled with idolatry since their beginnings, even after they agreed with their words that it was wrong. Their hearts were not in the right place, and Moses reiterates many times throughout Deuteronomy that they are prone to fall into idolatry again. One of the main reasons for this is that the nations all around them worshipped gods of wood and stone, and they believed this was necessary for the fertility of the land. People tend to be affected by the culture around them, even if they are not intentionally going down that road. People are also attracted by legalistic things they think will give them salvation.
Idolatry can take many forms, not just making images, and Moses hints at this as well. Rebellion in the heart, and betrayal by giving the greatest affection to another other than God, also constitute idolatry. Each person must examine their own hearts and situations because idolatry is so pervasive and individualized that it is easily missed or misinterpreted. Even Moses himself struggles to see his sin in the proper perspective. When retelling the reason why he will not enter Canaan, he blames the people rather than himself, both here and in his final sermon. And yet, while the people provoked him, the fault for his rebellious act lies totally on his shoulders (Num. 20:1–13). It is always a great temptation to blame others for our sins, rather than taking responsibility and owning it and then repenting and turning away from our rebellion.
And yet, Yahweh is exceedingly merciful in dealing with His erring and rebellious children. While there are consequences to our sins, God does not ever give up on us and is always seeking to bring us back. God is a jealous God, full of consuming fire, but this is because He loves us passionately and is a personal God. Rather than standing aside as a tyrant who just wants us to obey, God is married to us and wants a heart relationship of love and commitment. When we betray Him, Yahweh is heartbroken and responds as one would expect a jilted lover to do, filled with jealousy as well as longing for restoration.