The tune of this beloved chant dates to the 5th-7th century AD, as part of the Gallican Rite of the Roman Catholic liturgy. The text is the last two verses of the medieval hymn Pange Lingua, written by St. Thomas Aquinas:
Tantum ergo Sacramentum
Et antiquum documentum novo cedat ritui:
Praestet fides supplementum sensuum defectui.
Genitori, Genitoque laus et iubilatio,
Salus, honor, virtus quoque sit et benedictio:
Procedenti ab utroque
Compar sit laudatio. Amen.
Let us therefore, bowing low,
Venerate so great a Sacrament;
And let the old law give way to the new rite;
Let faith afford assistance to the deficiency of the senses.
To the Begetter and the Begotten let there be praise and jubilation,
Salvation and honor, and power and blessing;
And to the One proceeding from both
Let there be equal praise.