Theophylact of Ohrid

This is evident from the fact that He sent His Only-Begotten Son into the world so that He might grant us true life and we might live through Him.

Commentary on 1 John ↗

Polycarp of Smyrna

Let us then continually persevere in our hope, and the earnest of our righteousness, which is Jesus Christ, "who bore our sins in His own body on the tree," "who did no sin, neither was guile found in His mouth," but endured all things for us, that we might live in Him. Let us then be imitators of His patience; and if we suffer for His name's sake, let us glorify Him. For He has set us this example in Himself, and we have believed that such is the case.

Epistle to the Philippians 8 ↗

Augustine of Hippo

"In this was manifested the love of God in us." Behold, in order that we may love God, we have exhortation. Could we love Him, unless He first loved us? If we were slow to love, let us not be slow to love in return. He first loved us; not even so do we love. He loved the unrighteous, but He did away the unrighteousness: He loved the unrighteous, but not unto unrighteousness did He gather them together: He loved the sick, but He visited them to make them whole. …

Ten Homilies on 1 John 7 ↗

Bede

In this God's love appeared in us, etc. As the Lord himself says: Greater love hath no man than this, that a man lay down his life for his friends (John XV); and thus the love of Christ for us is proven, because he died for us. The Father's love is also proven in us, because he sent his only Son to die for us. Thus also the Apostle Paul says: He that spared not his own Son, but delivered him up for us all, how shall he not also with him freely give us all things (Rom. VIII)?

Commentary on the Catholic Epistles ↗