'Thirty' in the Bible

And three of the thirty chiefs went down toward the rock to David at the cave of Adullam when the army of the Philistines was encamped in the valley of Rephaim.

He himself was certainly distinguished among the thirty, but he did not attain to the three. And David appointed him over his bodyguard.

Adina the son of Shiza the Reubenite, a leader of the Reubenites, and thirty with him,

Ishmaiah the Gibeonite, a mighty warrior among the thirty [who was] over the thirty; Jeremiah; Jahaziel; Johanan; Jozabad the Gederathite;

Then the Spirit came upon Amasai, chief of the thirty [who said]: "[We are] yours, O David! And [we are] with you, O son of Jesse! Peace! Peace to you, and peace to those who help you, for your God helps you." So David appointed them as heads of the troops.

Of the sons of Gershom: Joel the chief and one hundred and thirty of his brothers.

And the Levites thirty years old and above were counted, and their number according to their head count for the men [was] thirty-eight thousand.

This [was] Benaiah [who was] a mighty warrior of thirty, and over the thirty and his working group [was] Ammizabad his son.