Have written. See on v. 12.
Fathers. Compare v. 13. The intimate knowledge of the Saviour that comes from long experience is the most important thing John can attribute to them. Those who have known God must also have known the Son, through whom alone God can be known (see on John 1:18).
Ye are strong. John expands his address to the young men. In v. 13 he records their victory over the devil. Now he reveals the enabling factor in that conquest (cf. Eph. 6:10-18).
Word of God. At first glance it might be thought that John here refers to the incarnate Word (cf. on John 1:1-3; 1 John 1:1-3). But it seems clear that he is here thinking of the written Word, the Holy Scriptures, which can “abide,” or be hidden, in the heart (John 15:7; Ps. 119:11).
The Word of God in the heart both inspires and equips the soldier of the cross to fight the good fight (see on Eph. 6:17). It reveals the fallen state of man, the craft and malice of Satan, the saving power of Christ exerted through the Holy Spirit, the high standard men are to reach through devotion to it, and the glorious reward of the overcomer. The Saviour Himself used the written Word in His struggle with the tempter (Matt. 4:1-11). Fighting man’s battle as a man, the Saviour had no keener weapon than the words which the Holy Spirit had inspired for just such occasions (Matt. 4:4, 7, 10). It is only as Christians follow Christ’s example, filling their memory with God’s precious Word and following its counsel, that they can gain the victory over self and sin.
Overcome. As with the fathers, John repeats his reason for commendation (cf. v. 13).