1 Samuel 17:20-22

He came to the trench Probably the carriages wherewith the host was surrounded. As the host was going forth to the fight Jesse little thought of sending his son to the camp just at that critical juncture. But the wise God orders the time and all the circumstances of affairs so as to serve the designs of his own glory. David left his carriage, &c. He left the provision which his father had sent his brethren with some proper person, it being not a time to present it to them when the armies were just going to engage. And ran into the army Eager to know what was doing there, being deeply concerned for the success of Israel, and desirous of seeing and speaking with his brethren before the commencement of the battle; for possibly it might be the last time he should ever converse with them or see them alive.