2 Kings 11:6

Let one third of you come in on the sabbath and keep guard, over the king’s house at the gate; another third at the gate of the highway, and the other third at the gate behind the guards. So you will guard the house.

Let a third part of you go in on the sabbath-day, and keep ye the watch of the king's house in the porch; and another third in the gate of the high way, and a third at the gate behind the footmen; and keep ye the guard of the house.