'Thirty' in the Bible

A son of thirty years is David in his being king; forty years he hath reigned;

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.

And David gathered again every chosen one in Israel, thirty thousand,

And three of the thirty heads go down and come unto the harvest, unto David, unto the cave of Adullam, and the company of the Philistines are encamping in the valley of Rephaim,

Of the thirty he is honoured, and unto the three he came not; and David setteth him over his guard.

Asahel brother of Joab is of the thirty; Elhanan son of Dodo of Beth-Lehem.

Uriah the Hittite; in all thirty and seven.