2 Samuel 5:4

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

1 Chronicles 26:31

Among the Hebronites was Jerijah the chief, even among the Hebronites, according to the genealogy of his fathers. In the fortieth year of the reign of David they were sought for, and there were found among them mighty men of valor at Jazer of Gilead.

1 Chronicles 29:27

And the time that he reigned over Israel was forty years; seven years reigned he in Hebron, and thirty and three years reigned he in Jerusalem.

Luke 3:23

And Jesus himself was about thirty years of age, being (as was supposed) the son of Joseph, who was the son of Heli,

1 Kings 2:11

And the days that David reigned over Israel were forty years: seven years reigned he in Hebron, and thirty and three years reigned he in Jerusalem.

1 Chronicles 3:4

These six were born unto him in Hebron; and there he reigned seven years and six months: and in Jerusalem he reigned thirty and three years.

Treasury of Scripture Knowledge

Summary

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

Thirty

Bible References

Thirty

Luke 3:23
And Jesus himself was about thirty years of age, being (as was supposed) the son of Joseph, who was the son of Heli,

Forty

1 Chronicles 26:31
Among the Hebronites was Jerijah the chief, even among the Hebronites, according to the genealogy of his fathers. In the fortieth year of the reign of David they were sought for, and there were found among them mighty men of valor at Jazer of Gilead.
1 Chronicles 29:27
And the time that he reigned over Israel was forty years; seven years reigned he in Hebron, and thirty and three years reigned he in Jerusalem.