'Thirty' in the Bible

Then he took me into the outer square, and there were rooms and a stone floor made for the open square all round: there were thirty rooms on the stone floor.

And the side-rooms, room over room, were three times thirty; there were inlets in the wall of the house for the side-rooms round about, for supports in the wall of the house.

In the four angles there were spaces walled in, forty cubits long and thirty wide; the four were of the same size.