In the end, it is not so much that David is great, but that the God he serves, the God who went before him, is great. Saul seems to focus on the size of the enemy rather than on the size of God. God always seems to give us enemies who are much greater than we are, so that we fight in our weakness, trusting in God and not in ourselves, giving Him the glory, rather than taking the credit ourselves.
When we come to David, we come to God’s chosen king. This is the one whose seed will be the promised Messiah, whose kingdom will have no end. And so David often provides us with a foreshadowing of Christ. Our text is no exception. David is a prototype of Christ, as Goliath is a prototype of Satan. Satan has the whole world trembling in fear of him and of death (see Hebrews 2:14-15). We, like the Israelites of old, are powerless to defeat him. What we cannot do for ourselves, Christ has done for us, just as David fought Goliath for Saul and the Israelites. Satan has a death grip on lost sinners. There is nothing we can do to save ourselves. Jesus came and took on Satan one-on-one, and He won the victory. David did it by killing Goliath. Jesus did it by being crucified on the cross of Calvary. But after He died to pay the penalty for our sins, He rose from the grave, triumphant over Satan, sin, and death. It was winner take all, and Jesus won by dying and by rising from the dead. All who acknowledge their sin, and who forsake trusting in themselves by placing their trust in Jesus Christ, have the forgiveness of sins and the assurance of living eternally in His kingdom. Thank God for our Champion, the Lord Jesus Christ.