1 Kings 2:39-46

2:39 Three years later two of Shimei’s servants ran away to King Achish son of Maacah of Gath. Shimei was told, “Look, your servants are in Gath.” 2:40 So Shimei got up, saddled his donkey, and went to Achish at Gath to find his servants; Shimei went and brought back his servants from Gath. 2:41 When Solomon was told that Shimei had gone from Jerusalem to Gath and had then returned, 2:42 the king summoned Shimei and said to him, “You will recall that I made you take an oath by the Lord, and I solemnly warned you, ‘If you ever leave and go anywhere, know for sure that you will certainly die.’ You said to me, ‘The proposal is acceptable; I agree to it.’ 2:43 Why then have you broken the oath you made before the Lord and disobeyed the order I gave you?” 2:44 Then the king said to Shimei, “You are well aware of the way you mistreated my father David. The Lord will punish you for what you did. 2:45 But King Solomon will be empowered and David’s dynasty will endure permanently before the Lord.” 2:46 The king then gave the order to Benaiah son of Jehoiada who went and executed Shimei.

So Solomon took firm control of the kingdom.