Romans 12:15
Rejoice with those who rejoice. Weep with those who weep.
WEB
Rejoice with them that do rejoice, and weep with them that weep.
KJV
What Romans 12:15 means
Paul gives the community a two-part instruction for love, to share other people's joy and to climb down into their grief, tying your emotional life to your neighbor's instead of standing at a polite distance.
This sits in a stretch of Paul's letter to the Romans where he rattles off short, practical instructions for how a community should treat one another: serve, give generously, show hospitality, bless, live in harmony. "Rejoice with those who rejoice; weep with those who weep" is two of them, easy to pass over because they sound so obvious. The form is blunt and memorable, almost a proverb.
The striking thing is the direction of the command. It is not addressed to the person who is suffering or celebrating; it is addressed to everyone around them. The one in grief is told nothing here. The community is told to come close. Weeping "with" someone is harder than weeping for them: it means stepping into a sorrow that is not yours and staying there without rushing to fix it. The first half is its own discipline, since sharing another's joy without envy can ask as much of us as sharing their grief.
Paul assumes love is something the whole room does, not a private feeling kept to yourself. Real community, in this vision, ties your emotional life to your neighbor's, so that no one carries joy or loss entirely alone. The instruction is short because it is meant to be acted on rather than admired. Often the only thing it leaves unsettled is whose joy or whose sorrow you are being asked to step into now.