I am writing to you, fathers, because you know Him who has been from the beginning. I am writing to you, young men, because you have overcome the evil one. I have written to you, children, because you know the Father.
The age distinctions referred to in this verse could refer as easily to spiritual maturity as to chronological age. Either way “fathers” would indicate mature believers. These elders had been long acquainted with the principles of the faith and understood well its doctrines and duties. Some readers of John’s age may have even heard the teachings from Jesus himself! Mature believers then and now possess a special responsibility to maintain true doctrine in the face of false teaching.
“Young men” usually referred to 20-40 year olds but could indicate those strong in their faith and no longer spiritual children. They were well-grounded in the truth and had been engaged in Christian warfare, overcoming the wicked one. Those with strength to fight the assaults of evil from within and without the body of believers must do so.
“Little children,” though young either in chronological age or in the faith, were acquainted with the principles of the faith and understood well its doctrines and duties. If all they could do was but to cry out to their Abba Father their sins were forgiven as they began their journey of faith. Wherever we are in our Christian walks, it is our responsibility to grow in Christ, fight against evil, and train those younger in the faith.