The Lord be with you
Below is an excerpt from one of the sermons of Caesarius of Arles, a Church Father renowned for his sermons. You will notice that he uses a type of interpretation called “allegorical,” though he doesn’t use that word here. This approach was very popular for the first fifteen hundred years of the Church’s history, but fell into disfavor by the end of the Reformation because it is easily abused. Caesarius, though, shows us how to use it well.
David came and found the Jewish people fighting against the Philistines [1 Samuel 17]. Since there was no one who dared to enter single combat, he who prefigured Christ went out to battle, and carrying a staff in his hand opposed Goliath. In him, was surely indicated what was fulfilled in our Lord Jesus Christ, for Christ the true David came and carried His cross with the purpose of fighting against the spiritual Goliath, that is, the devil. Notice where blessed David struck Goliath, brethren: on the forehead where there was no sign of the cross. Just as the staff typified the cross, so the stone with which he was struck prefigured Christ our Lord, for He is the living stone of which it is written: ““The stone which the builders rejected has become the cornerstone.” [Psalm 117:22] The fact that without a sword David stood over Goliath and killed him with his own sword, shows that at the coming of Christ the devil was defeated with his own sword. Indeed, by the wickedness and unjust persecution which he practiced toward Christ, the devil lost his power over all those who believed him, David put the arms [weapons] of Goliath in his tent, and we were the arms of the devil, for thus the Apostle speaks: “As you yielded your members to sin as weapons of iniquity, so now yield your members to God as weapons of justice” [Rom. 6:19]; and again: “Do not yield your members to sin as weapons of iniquity.” [Rom. 6:13] Christ, indeed, put the arms of our enemy in His tent when we who had been the house of the devil merited to become the temple of God through His grace, for we are known to dwell in Christ and He lives in us. The Apostle proves that Christ dwells within us when he says: “Have Christ dwelling through faith in the inner man” [Eph. 3:16-17]; and the same Apostle shows again that we live in Christ by saying: “All you who have been baptized into Christ, have put on Christ.” [Gal. 3:27] Our Lord further tells His disciples in the Gospel: “I am in my Father, and you in me, and I in you.” [John 14:20]
The fact that Goliath was not struck in any other member but the forehead signifies something that happens in our own case. When a catechumen is signed on the forehead the spiritual Goliath is struck, the devil is routed.
Caesarius of Arles (470-542) Sermons, Vol. II
My source: For All the Saints, volume II, Year 1 (302-303)
Blessings in Christ