I Samuel 17:54 And David took the head of the Philistine, and brought it to Jerusalem; but he put his armour in his tent.
David took the head and traveled to Jerusalem. Imagine the scene: David has killed the giant. He has taken his head. He will show it to Saul and the army of the Lord.
He then travels with it to show to the nation what God can do with one man that will trust him and run to the battle. God has shown His power.
David has proven that God can over other gods. David has proven that the youth can be used when all disdained him.
What is on the inside is starting to show on the outside. That head will win the hearts of the nation and his dearest earthly friend, Jonathan.
As you go out to do battle dear missionary prepare to fight the giant. When you defeat him more enemies will come but so will the army that God will give you to win great battle for Him.