1 Chronicles 19:6

But the princes of the children of Ammon said to Hanun, “Do you think that David honors your father, in that he has sent comforters to you? Haven’t his servants come to you to search, to overthrow, and to spy out the land?”

So Hanun took David’s servants, shaved them, and cut off their garments in the middle at their buttocks, and sent them away.

Then some people went and told David how the men were treated. He sent to meet them; for the men were greatly humiliated. The king said, “Stay at Jericho until your beards have grown, and then return.”

So they hired for themselves thirty-two thousand chariots, and the king of Maacah with his people, who came and encamped near Medeba. The children of Ammon gathered themselves together from their cities, and came to battle.

When David heard of it, he sent Joab with all the army of the mighty men.

The children of Ammon came out, and put the battle in array at the gate of the city; and the kings who had come were by themselves in the field.