When Prophet Samuel anointed David as the king of Israel, the Spirit of God came upon David. In the New Testament, the Spirit of God is described as the Spirit with which we are sealed till the day of redemption (see Ephesians 4 vs. 30). So David was anointed as king, and the Spirit that also serves as a seal was released upon him. He did not just receive the oil for the throne; he also received the seal that made him untouchable.
Friend, hear me as I hear the Lord: if you have received the Spirit of God in you, then God has placed a seal upon you; God has placed a seal upon your family; God has placed a seal upon your finances; God has placed a seal on your health; God has placed a seal on your career; God has placed a seal on the works of your hands; God has placed a seal on everything that concerns you; you are sealed beyond the reach of the enemy.
Go and announce to those who imagine that you are vulnerable: they can only try to hurt you, but they will never succeed because of the seal of the Spirit on your life. You have no reason to be afraid of the snares of predators and marauders. You have no reason to be afraid of those who are making evil plans against you. You have no reason to be afraid of the wickedness of the wicked. They can only try, but you are sealed.
David would eventually go on to fight several battles as king, but though he may have come close to danger sometimes, no one was able to kill David in war. No one was able to cut down David to death. Hear me as I hear the Lord: because of the seal of the Spirit of God upon your life, no battle that comes your way will consume you. No trap of the enemy will catch you. No wicked attack of hell will swallow you.
The seal of the Lord is upon you, and if the Lord has sealed you, no devil and no enemy can unseal you.