1 Chronicles 29:27

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

2 Samuel 5:4-5

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

1 Kings 2:11

The days that David reigned over Israel were forty years; he reigned seven years in Hebron, and he reigned thirty-three years in Jerusalem.

1 Chronicles 3:4

six were born to him in Hebron; and there he reigned seven years and six months. In Jerusalem he reigned thirty-three years;

Treasury of Scripture Knowledge

Summary

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.

Bible References

Forty years

1 Chronicles 3:4
six were born to him in Hebron; and there he reigned seven years and six months. In Jerusalem he reigned thirty-three years;
2 Samuel 5:4
David was thirty years old when he began to reign, and he reigned forty years.
1 Kings 2:11
The days that David reigned over Israel were forty years; he reigned seven years in Hebron, and he reigned thirty-three years in Jerusalem.