Why did David choose five smooth stones?

³⁹ David girded his sword over his armor and tried to walk, for he had not tested them. So David said to Saul, “I cannot go with these, for I have not tested them.” And David took them off. ⁴⁰ He took his stick in his hand and chose for himself five smooth stones from the brook, and put them in the shepherd’s bag which he had, even in his pouch, and his sling was in his hand; and he approached the Philistine. (1 Samuel 17:39-40)

At the end of Elisha’s life, he instructs the king to do a series of tasks, leading up to this.

¹⁸ Then he said, “Take the arrows,” and he took them. And he said to the king of Israel, “Strike the ground,” and he struck it three times and stopped. ¹⁹ So the man of God was angry with him and said, “You should have struck five or six times, then you would have struck Aram until you would have destroyed it. But now you shall strike Aram only three times.” (2 Kings 13:18-19)

David was chosen for being a man after God’s own heart (1 Samuel 13:14), and Elisha requested a double portion of the spirit that was on Elijah (2 Kings 2:9). So, I believe David knew his equipment, even though he trusted God, and he knew it might take five to make sure it was complete.

¹⁷ She said, “These six measures of barley he gave to me, for he said, ‘Do not go to your mother-in-law empty-handed.’” ¹⁸ Then she said, “Wait, my daughter, until you know how the matter turns out; for the man will not rest until he has settled it today.” (Ruth 3:17-18)

References

1 Samuel 17:39-40

2 Kings 13:18-19

1 Samuel 13:14

2 Kings 2:9

Ruth 3:17-18

1 Kings 19:14-19