1 Samuel 17:14

And David, he the small; and the three great ones went after Saul.

1 Samuel 16:11

And Samuel will say to Jesse, Are these the whole of the boys? And he will say, The small was yet left, and behold, he fed among the sheep. And Samuel will say to Jesse, Send and take him, for we will not turn about till his coming here.

Genesis 25:23

And Jehovah will say to her, Two nations are in thy womb, and two peoples shall be separated from thy belly: and a people shall be strong above a people, and the great shall serve the small.

Treasury of Scripture Knowledge

Summary

And David was the youngest: and the three eldest followed Saul.

Bible References

The youngest

1 Samuel 16:11
And Samuel will say to Jesse, Are these the whole of the boys? And he will say, The small was yet left, and behold, he fed among the sheep. And Samuel will say to Jesse, Send and take him, for we will not turn about till his coming here.
Genesis 25:23
And Jehovah will say to her, Two nations are in thy womb, and two peoples shall be separated from thy belly: and a people shall be strong above a people, and the great shall serve the small.