For he did put his life in his hand
Exposed himself to the utmost danger, when no one in all the camp of Israel would do the like:
and slew the Philistine;
Goliath of Gath, who defied the armies of Israel; against him he went unarmed, only with his sling and stones, and fought him, and slew him:
and the Lord wrought a great salvation for all Israel;
by his hand, so that they were delivered from their enemies, who fled before them, and they pursued them, and got a complete victory over them:
thou sawest [it], and didst rejoice;
he was an eyewitness of David's going forth against the Philistine, and slaying him, and of all the happy effects of it, which then greatly affected him, and he could not forbear expressing great joy on that occasion:
wherefore then wilt thou sin against innocent blood, to slay David
without a cause?
and so entail the guilt of it on himself and family.