1 Kings 11:24

And he gathered men unto him, and became captain over a band, when David slew them of Zobah: and they went to Damascus, and dwelt therein, and reigned in Damascus.

Rezon gathered men to himself and became captain and leader over a band. This gathering took place when David defeated and slew the men of Zobah. He then went to Damascus, settled and dwelt there, and reigned and ruled there over Syria. The verse belongs to the account in 1 Kings 11:14-28 that records the adversaries raised against Solomon. Rezon was one of those adversaries, whom God raised up and permitted to trouble Solomon and weaken his kingdom as judgment after Solomon's disobedience and unfaithfulness.