In addition to wanting their people to worship only Yahweh, these Priestly writers wanted to turn them against other gods. To further unite the Israelites, they wrote through the voice of Yahweh, commanding the Israelites to destroy their enemies, forbidding them to intermarry with non-Israelites, and commanding them to
destroy any Israelite that would ever intermarry. Yahweh further commanded them to destroy the temples and images of competing gods. Lastly, to make them feel special and distinct from non-Israelites, Yahweh claims that they are his chosen people.
Here is the message from the Priestly writers speaking as the new version of their god, Yahweh, in Deuteronomy 7:1-6:
“When the Lord your God brings you into the land that you are about to enter and occupy, and he clears away many nations before you—the Hittites, the Girgashites, the Amorites, the Canaanites, the Perizzites, the Hivites, and the Jebusites, seven nations mightier and more numerous than you—and when the Lord your God gives them over to you, and you defeat them, then you must utterly destroy them. Make no covenant with them and show them no mercy. Do not intermarry with them, giving your daughters to their sons or taking their daughters for your sons, for that would turn away your children from following me, to serve other gods. Then the anger of the Lord would be kindled against you, and he would destroy you quickly. But this is how you must deal with them: break down their altars, smash their pillars, hew down their sacred poles, and burn their idols with fire. For you are a people holy to the Lord your God; the Lord, your God, has chosen you out of all the peoples on earth to be his people, his treasured possession. (Deuteronomy 7:1-6 )” [italics for emphasis]