So, God does have favorites, at least within the house of Israel during a time of crisis. As we have seen in the previous chapters the people of God have turned their back on Him time after time. There is no one in the land who has obeyed the Lord, until you get to the Rechabites. Who are the Rechabites? They are a tribe of Israel, much like the Nazarenes, who promised not to drink wine or hard drink while they served the Lord.
So God uses them as an object lesson. He tells Jeremiah to bring them and all of their families into the temple, the place where God resides. Bring them in and offer them wine and tell them to drink wine. Jeremiah does that and the head of the household said we will not drink wine because we promised God that we would not drink wine all the days of our lives. So even though a prophet of the Lord offered them wine in the house of the Lord, which you would think would trump the tradition of not drinking, they still obeyed the Lord instead of falling prey to that which was in front of them at that time.
The lesson the people of Israel were supposed to learn was the one seen in vs.13: "Can you not learn a lesson and obey my words?" And then again we read: "The descendants of Jonadab son of Rechab have carried out the command that their ancestor gave them, but this people has not obeyed me." As a result this family will never lack a descendant in their midst. So they have that going for them. Which is nice.