The Apostle Paul
Romans 12:15BSB·traditional attribution

Rejoice with those who rejoice; weep with those who weep.

John Calvin Reformed @genevareformer

15. Rejoice with those who rejoice, etc. A general truth is in the third place laid down, — that the faithful, regarding each other with mutual affection, are to consider the condition of others as their own. He first specifies two particular things, — That they were to “rejoice with the joyful, and to weep with the weeping.” For such is the nature of true...

Matthew Henry Presbyterian @wholebiblehenry

We may observe here, according to the scheme mentioned in the contents, the apostle's exhortations, I. Concerning our duty to God, We see what is godliness. 1. It is to surrender ourselves to God, and so to lay a good foundation. We must first give our own selves unto the Lord, Co2 8:5. This is here pressed as the spring of all duty and obedience, Rom 12:1, Rom 12:2.

Commenting on Romans 12:1-21

John Gill Reformed Baptist @doctorgill

Rejoice with them that do rejoice,.... Not in anything sinful and criminal, in a thing of nought, in men's own boastings; all such rejoicing is evil, and not to be joined in; but in things good and laudable, as in outward prosperity; and to rejoice with such, is a very difficult task; for unless persons have a near concern in the prosperity of others, they...