141 Joab could see that David was upset about Absalom.
2-3 So he fetched a wise woman from Tekoah. He told her to pretend to have been mourning for a long time. Then he sent her to David and told her what to say.
I’m a widow with two sons. One of my sons killed the other. And my whole family has demanded that I deliver my son to them, so they can kill him for killing his brother.
When you become his servant, tell Zadok and Abiathar whatever you hear.
37 So Hushai returned to Jerusalem and became David's spy.
A few more words about this episode
Absalom's hair weighed more than 200 shekels (14:26)
Each year, when Absalom's hair was cut, the weight of the cut hair was 200 shekels, which would be about 2 kilograms. Absalom's hair was heavy upon him
After forty years (15:7)
After forty years! Some translations say "four years" - probably to remove the obvious absurdity.
David's counselor, Ahithophel (15:12)
This is the first mention of Ahithophel in the Bible. He was David's counselor but left him for Absalom. Wikipedia: Ahithophel
Then Hushai came (15:32)
This is the first time Hushai is mentioned in the Bible. He will be one of David's spies on Absalom's conspiracy. Wikipedia: Hushai
Zadok and Abiathar (15:33)
Zadok and Abiathar were priests. This is also the first time that Zadok is mentioned in the Bible. Abiathar was the son of Ahimelech and was the only priest to escape Saul's massacre of Nob. (1 Samuel 22:6-23, Episode 112)
Wikipedia: Zadok, Abiathar