'Thirty' in the Bible

Also he made the molten sea of ten cubits from brim to brim, round in compass; and its height was five cubits; and a line of thirty cubits encircled it.

But Jehoiada grew old and was full of days, and he died; one hundred thirty years old was he when he died.

Josiah gave to the children of the people, of the flock, lambs and young goats, all of them for the Passover offerings, to all who were present, to the number of thirty thousand, and three thousand bulls: these were of the king's substance.