6 “I write unto you, young men.” There are sons, are fathers, are young men: sons, because begotten; fathers, because they acknowledge the Beginning; why young men? “Because you have overcome the wicked one.” In the sons, birth: in the fathers, antiquity: in the young men, strength. If the wicked one is “overcome” by the young men, he fights with us. Fights, but not conquers. Wherefore? Because we are strong, or because He is strong in us who in the hands of the persecutors was found weak? He has made us strong, who resisted not His persecutors. “For He was crucified of weakness, but He lives by the power of God.”
Source: Homilies on the First Epistle of John (New Advent)