David thought, “I will show kindness to Hanun son of Nahash, because his father showed kindness to me.” So David sent a delegation to express his sympathy to Hanun concerning his father. When David’s envoys came to Hanun in the land of the Ammonites to express sympathy to him,
the Ammonite commanders said to Hanun, “Do you think David is honoring your father by sending envoys to you to express sympathy? Haven’t his envoys come to you only to explore and spy out the country and overthrow it?”
References for 1 Chronicles 19:3
So Hanun seized David’s envoys, shaved them, cut off their garments at the buttocks, and sent them away.
When someone came and told David about the men, he sent messengers to meet them, for they were greatly humiliated. The king said, “Stay at Jericho till your beards have grown, and then come back.”
When the Ammonites realized that they had become obnoxious to David, Hanun and the Ammonites sent a thousand talents of silver to hire chariots and charioteers from Aram Naharaim, Aram Maakah and Zobah.
References for 1 Chronicles 19:6
They hired thirty-two thousand chariots and charioteers, as well as the king of Maakah with his troops, who came and camped near Medeba, while the Ammonites were mustered from their towns and moved out for battle.
References for 1 Chronicles 19:7
On hearing this, David sent Joab out with the entire army of fighting men.
The Ammonites came out and drew up in battle formation at the entrance to their city, while the kings who had come were by themselves in the open country.
Joab saw that there were battle lines in front of him and behind him; so he selected some of the best troops in Israel and deployed them against the Arameans.
He put the rest of the men under the command of Abishai his brother, and they were deployed against the Ammonites.
References for 1 Chronicles 19:11
Joab said, “If the Arameans are too strong for me, then you are to rescue me; but if the Ammonites are too strong for you, then I will rescue you.