1 Samuel 17:22
And David left his carriage in the hand of the keeper of the carriage, and ran into the army, and came and saluted his brethren. And David left his carriage in the hand of the keeper of the carriage, and ran into the army, and came and saluted his brethren.
David left the supplies and belongings he had brought in the care of the keeper in charge of them. Having left them, he ran to the Israelite army and greeted his brothers, coming among them where they stood. He had come on a humble errand at his father Jesse's direction, to carry a message and a gift to his brothers and to learn whether they were safe.
He had also been directed by an angel to save Israel. He reached the army just as Goliath was issuing his challenge to Israel, which he heard only after he arrived. Upon arriving and hearing it, his concern for God's honor and for his people was stirred.
His story in this setting holds up humility and trust in God rather than reliance on human weapons or self-confidence. The particular act of coming to his brothers stands without separate explanation or application beyond that larger lesson.