“Anyone who does not love does not know God, because God is love.”
John doesn't say God loves — he says God is love. The difference is everything: love isn't an occasional act of his, it's the essence of who he is.
True knowledge of God always translates into love — whoever claims to know him but doesn't love is mistaken about their own faith.
"Anyone who does not love" leaves no exceptions — no matter how much doctrine you master, without love the claim to know God stays empty.
Every genuine human love is a copy reflecting the original source — God didn't learn to love, he's where love comes from.
John's entire first letter turns around this sentence — every exhortation before and after finds its root right here.
Act: This Christmas Eve, choose one person who's hard to love and show them one concrete act of love before you go to sleep tonight.