When the words that David spoke were heard, they repeated them before Saul, and he sent for him.
David is at length presented to Saul for his champion (Sa1 17:31) and he bravely undertakes to fight the Philistine (Sa1 17:32): Let no man's heart fail because of him. It would have reflected too much upon the valour of his prince if he had said, Let not thy heart fail; therefore he speaks generally: Let no man's heart fail.
Commenting on 1 Samuel 17:31-39
And when the words were heard which David spake,.... To one, and to another, and these reported to other persons, and so they went from one to another through many hands: they rehearsed them before Saul; coming to the ears of some of his courtiers and counsellors, or officers about him, they told him what such an one had said: and he sent for him...
1Sa 17:31 David’s words were told to Saul, who had him sent for immediately.