1 Kings 2:11

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

2 Samuel 5:4-5

Thirty years old, was David when he began to reign, - forty years, he reigned:

1 Chronicles 29:26-27

Thus, David son of Jesse, reigned over all Israel;

Treasury of Scripture Knowledge

Summary

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.

Bible References

Reigned over

2 Samuel 5:4
Thirty years old, was David when he began to reign, - forty years, he reigned:
1 Chronicles 29:26
Thus, David son of Jesse, reigned over all Israel;