'Twelve' in the Bible

The two pillars, the great water-vessel, and the twelve brass oxen which were under it, and the ten wheeled bases, which King Solomon had made for the house of the Lord: the brass of all these vessels was without weight.

And as for the pillars, one pillar was eighteen cubits high, and twelve cubits measured all round, and it was as thick as a man's hand: it was hollow.