John Gill emphasizes the importance of spiritual strength and vigilance among both the aged and young believers in Christ. He encourages the fathers to remain zealous and not become indifferent, reminding them of their deep knowledge of God from the beginning. For the young men, he highlights their strength in Christ and the necessity of abiding in the Word of God to overcome temptations and the wicked one. Gill stresses that true strength comes not from oneself but through Christ, who empowers believers to fulfill their duties and resist sin.

Ver. 14. I have written unto you, fathers,.... This, with the reason annexed to it, is repeated, to raise the attention of the aged servants of Christ, and to quicken them to a discharge of their duty, who are apt to abate in their zeal, to grow lukewarm and indifferent, to cleave to the world, and to the things of it, which they are cautioned against in 1Jo 2:15. The whole of this, with the reason, because ye have known him [that is] from the beginning, is left out in the Vulgate Latin version, and Complutensian edition. I have written unto you, young men; this repetition to them, with some additions, is also made, to stir them up the more to love the saints, who are too apt to be carried away with the lust of the flesh, the lust of the eyes, and the pride of life, warned against in 1Jo 2:16; because ye are strong; not naturally, for sin has sadly weakened human nature, so that a man, by the strength of nature, can do nothing that is spiritually good: nor in themselves, though regenerated, but in Christ, in whom are righteousness and strength; without whom they can do nothing, though they can do all things through him strengthening them; and so are strong in the exercise of grace on him, and in the performance of every duty, being strengthened by him with strength in their souls: and the word of God abideth in you; either Christ the Logos, the essential Word of God, who might be said to be in them, and abide in them, because his grace was implanted in their hearts, called Christ, formed there, and because he dwelt in their hearts by faith, and lived in them; and hence they had their strength, or came to be so strong as they were, and also overcame Satan, because he that was in them was greater than he that is in the world: or else the Gospel is meant, which cometh not in word only, but in power, has a place in the heart, and works effectually, and dwells richly there; and this is a means of spiritual strength against sin and temptation, and to perform duty, and to stand fast in the truth against the errors and heresies of men and is that piece of spiritual armour, the sword of the Spirit, by which Satan is often foiled, and overcome: hence it follows, and ye have overcome the wicked one; See Gill on "1Jo 2:13".