'Thirty' in the Bible

David was thirty years old when he began to reign, and he reigned forty years.

In Hebron he reigned over Judah seven years and six months: and in Jerusalem he reigned thirty and three years over all Israel and Judah.

Again, David gathered together all the chosen men of Israel, thirty thousand.

And three of the thirty chief went down, and came to David in the harvest time unto the cave of Adullam: and the troop of the Philistines pitched in the valley of Rephaim.

He was more honourable than the thirty, but he attained not to the first three. And David set him over his guard.

Asahel the brother of Joab was one of the thirty; Elhanan the son of Dodo of Bethlehem,

Uriah the Hittite: thirty and seven in all.