Fights are Necessary to Prove our Faith
As we approach then, dearly-beloved, the beginning of Lent, which is a time for the more careful serving of the Lord, because we are, as it were, entering on a kind of contest in good works, let us prepare our souls for fighting with temptations, and understand that the more zealous we are for our salvation, the more determined must be the assaults of our opponents.
But "stronger is He that is in us than He that is against us," (1 John 4:4) and through Him are we powerful in whose strength we rely: because it was for this that the Lord allowed Himself to be tempted by the tempter, that we might be taught by His example as well as fortified by His aid. For He conquered the adversary, as you have heard , by quotations from the law, not by actual strength, that by this very thing He might do greater honour to man, and inflict a greater punishment on the adversary by conquering the enemy of the human race not now as God but as Man. He fought then, therefore, that we too might fight thereafter: He conquered that we too might likewise conquer.
For there are no works of power, dearly-beloved, without the trials of temptations, there is no faith without proof, no contest without a foe, no victory without conflict.
This life of ours is in the midst of snares, in the midst of battles; if we do not wish to be deceived, we must watch: if we want to overcome, we must fight. And therefore the most wise Solomon says, "My son in approaching the service of God prepare your soul for temptation." (Sirach 2:1)
For “He being a man full of the wisdom of God, and knowing that the pursuit of religion involves laborious struggles, foreseeing too the danger of the fight, forewarned the intending combatant; lest haply, if the tempter came upon him in his ignorance, he might find him unready and wound him unawares."
The Christian's armour is both for defense and for attack
So, dearly-beloved, let us who instructed in Divine learning come wittingly to the present contest and strife, hear the Apostle when he says, "for our struggle is not against flesh and blood, but against principalities and powers, against the rulers of this dark world, against spiritual wickedness in heavenly things," (Ephesians 6:12) and let us not forget that these our enemies feel it is against them all is done that we strive to do for our salvation, and that by the very fact of our seeking after some good thing we are challenging our foes.
For this is an old-standing quarrel between us and them fostered by the devil's ill-will, so that they are tortured by our being justified, because they have fallen from those good things to which we, God helping us, are advancing. If, therefore, we are raised, they are prostrated: if we are strengthened, they are weakened. Our cures are their blows, because they are wounded by our wounds' cure. "Stand, therefore", dearly-beloved, as the Apostle says, "having the loins of your mind girt in truth, and your feet shod in the preparation of the gospel of peace, in all things taking the shield of faith in which you may be able to extinguish all the fiery darts of the evil one, and put on the helmet of salvation and the sword of the Spirit, which is the Word of God. (Ephesians 6:14-17)
See, dearly-beloved, with what mighty weapons, with what impregnable defences we are armed by our Leader, who is famous for His many triumphs, the unconquered Master of the Christian warfare.
He has girt our loins with the belt of chastity, He has shod our feet with the bonds of peace: because the unbelted soldier is quickly vanquished by the suggester of immodesty, and he that is unshod is easily bitten by the serpent.
He has given the shield of faith for the protection of our whole body; on our head has He set the helmet of salvation; our right hand has He furnished with a sword, that is with the word of Truth: that the spiritual warrior may not only be safe from wounds, but also may have strength to wound his assailant.
Taken from the Sermons of Pope St. Leo the Great, Sermon 39