Whoever does not love does not know God, because God is love.
The Greek aorist means he has never once known God, not merely that he does not know Him now. God is not merely loving but fundamentally and essentially Love itself. If love were only one attribute among others, the argument would fail, he might know God through His other qualities. But since love is His very essence, one who does not love knows not God at all.
AI summary
The confirmation lies in God's nature itself: to love men. The supreme proof is this, that of His own free and infinite good will toward us His enemies, He delivered not some common man but His only begotten Son to death, so that we, reconciled through His blood, might become partakers of His everlasting glory.
AI summary
To claim love for God whom you have never seen while refusing to love His visible children is a contradiction that cannot stand. God is love itself: the three divine Persons in eternal, inexpressible affection for one another; He bears unchangeable love to His elect in Christ; and from His breast flows nothing but love. The saints must love one another because they are His children, born of Him, and must be like their heavenly Father.
AI summary