Romans 12:15

Tertullian On Idolatry

The first point, indeed, on which I shall join issue is this: whether a servant of God ought to share with the very nations themselves in matters of his kind either in dress, or in food, or in any other kind of their gladness. "To rejoice with the rejoicing, and grieve with the grieving,"[93]

Tertullian On Fasting

know not easily how to sing, except when you are supping with a goodly company!) But those conclaves first, by the operations of Stations and fastings, know what it is "to grieve with the grieving," and thus at last "to rejoice in company with the rejoicing."[95]