Tantum ergo are the opening words of the last two verses of Pange Lingua, a Mediaeval Latin

Latin

Latin is an Italic language originally spoken in Latium and Ancient Rome. It, along with most European languages, is a descendant of the ancient Proto-Indo-European language. Although it is considered a dead language, a number of scholars and members of the Christian clergy speak it fluently, and...

 hymn

Hymn

A hymn is a type of song, usually religious, specifically written for the purpose of praise, adoration or prayer, and typically addressed to a deity or deities, or to a prominent figure or personification...

 written by St Thomas Aquinas. These last two verses are sung during veneration and Benediction of the Blessed Sacrament

Benediction of the Blessed Sacrament

Benediction of the Blessed Sacrament is a devotional ceremony celebrated within the Latin Rite of the Roman Catholic Church, as well as in some Anglican and Lutheran Churches, Liberal Catholic churches, Western Rite Orthodox churches, and Latinised Eastern Catholic Churches.Benediction of the...

 in the Roman Catholic Church

Roman Catholic Church

The Catholic Church, also known as the Roman Catholic Church, is the world's largest Christian church, with over a billion members. Led by the Pope, it defines its mission as spreading the gospel of Jesus Christ, administering the sacraments and exercising charity...

 and other churches that practice this devotion. It is usually sung, though solemn recitation

Recitation

A recitation is a presentation made by a student to demonstrate knowledge of a subject or to provide instruction to others. In some academic institutions the term is used for a presentation by a teaching assistant or instructor, under the guidance of a senior faculty member, that supplements...

 is sometimes done, and permitted.

Latin text

Tantum ergo Sacramentum

Veneremur cernui:

Et antiquum documentum

Novo cedat ritui:

Praestet fides supplementum

Sensuum defectui.



Genitori, Genitoque

Laus et jubilatio,

Salus, honor, virtus quoque

Sit et benedictio:

Procedenti ab utroque

Compar sit laudatio.

Amen.



V. Panem de caelis praestitisti eis.(T.P. Alleluja)

R. Omne delectamentum in se habentem.(T.P. Alleluja)



Oremus

Oremus

Oremus is the invitation to pray, said before short prayers in the Roman Catholic Mass and the Lutheran Divine Service, as well as other Western liturgies....

: Deus, qui nobis sub sacramento mirabili, passionis tuae memoriam reliquisti: tribue, quaesumus, ita nos corporis et sanguinis tui sacra mysteria venerari, ut redemptionis tuae fructum in nobis iugiter sentiamus. Qui vivis et regnas in saecula saeculorum

In saecula saeculorum

The Latin phrase expresses the idea of eternity. It is biblical, taken from the Vulgate translation of the New Testament, rendering Greek . The usual English translation is "for ever and ever", but in Ephesians 3:21, the KJV notably has "world without end"...

.

R. Amen.

English translation

A translation over a hundred years old and still used in Catholic churches liturgically renders the hymn thus, in a form which can be sung to the same music as the Latin:

Down in adoration falling,

Lo! the sacred Host we hail,

Lo! o'er ancient forms departing

Newer rites of grace prevail;

Faith for all defects supplying,

Where the feeble senses fail.

To the everlasting Father,

And the Son Who reigns on high

With the Holy Ghost proceeding

Forth from Each eternally,

Be salvation, honor, blessing,

Might and endless majesty.

Amen.

V. Thou hast given them bread from heaven.

R. Having within it all Sweetness.

V. Let us pray: O God, who in this wonderful Sacrament left us a memorial of Thy Passion: grant, we implore Thee, that we may so venerate the sacred mysteries of Thy Body and Blood, as always to be conscious of the fruit of Thy Redemption. Thou who livest and reignest forever and ever.

R. Amen.

Other, more modern English translations, such as this one, exist and are also used in Catholic churches liturgically.

Literal Translation

Hence so great a Sacrament

Let us venerate with heads bowed [cernui]

And let the old practice [documentum]

Give way to the new rite;

Let faith provide a supplement

For the failure of the senses.

To the Begetter and the Begotten [both masculine gender],

Be praise and jubilation,

Hail, honor, virtue also,

And blessing too:

To the One proceeding from Both

Let there be equal praise.

Amen.

V. You have appointed for them [less literally, determined for them to have] bread from heaven.

R. Having in itself [in se] all delight [delectamentum].

V. Let us pray: O God, who to us in this wonderful Sacrament, bequeathed a memorial of your Passion: grant, we beseech, that we, in worshiping [venerari; in addition to simple worship, may also mean worshiping in order to receive favor] the Holy Mysteries of your body and blood, may within ourselves continually [iugiter], sensibly perceive [sentiamus] the fruit of your redemption. You who live and reign into ages of ages.

R. Amen.

Theological Aspects

The words "procedenti ab utroque / compar sit laudatio"--literally, "May equal praise be to the One proceeding from both"--refer to the Holy Spirit

Holy Spirit

Holy Spirit is a term introduced in English translations of the Hebrew Bible, but understood differently in the main Abrahamic religions.While the general concept of a "Spirit" that permeates the cosmos has been used in various religions Holy Spirit is a term introduced in English translations of...

, who according to the later version of the Nicene Creed

Nicene Creed

The Nicene Creed is the creed or profession of faith that is most widely used in Christian liturgy. It is called Nicene because, in its original form, it was adopted in the city of Nicaea by the first ecumenical council, which met there in the year 325.The Nicene Creed has been normative to the...

 used in Western Christianity

Western Christianity

Western Christianity is a term used to include the Latin Rite of the Catholic Church and groups historically derivative thereof, including the churches of the Anglican and Protestant traditions, which share common attributes that can be traced back to their medieval heritage...

 proceeds from both the Father and the Son (see Filioque). Many Eastern Christians

Eastern Christianity

Eastern Christianity comprises the Christian traditions and churches that developed in the Balkans, Eastern Europe, Asia Minor, the Middle East, Northeastern Africa, India and parts of the Far East over several centuries of religious antiquity. The term is generally used in Western Christianity to...

do not share this belief that the Spirit proceeds from both the Father and the Son.