Ubi Caritas is an ancient chant, thought to have originated in France between the 4th and 10th century (source). The original text has several stanzas. Here is the first stanza with English translation:

Ubi caritas et amor, Deus ibi est.
Congregavit nos in unum Christi amor.
Exultemus, et in ipso iucundemur.
Timeamus, et amemus Deum vivum.
Et ex corde diligamus nos sincero.

Where charity and love are, God is there.
Christ's love has gathered us into one.
Let us rejoice and be pleased in Him.
Let us fear, and let us love the living God.
And may we love each other with a sincere heart. 

(source)