Adoro te devote

"Adoro te devote" is a Eucharistic hymn written by Thomas Aquinas. Adoro te devote is one of the five Eucharistic hymns, which were composed and set to music for the Solemnity of Corpus Christi, instituted in 1264 by Pope Urban IV as a Solemnity for the Latin Church of the Catholic Church.
Since the beginning of its composition and it being set to music, Adoro te devote was chanted as an Eucharistic Hymn during the Saint Mass "in honorem SS. Sacramenti" (in honour of the Most Blessed Sacrament), as it was written in the Latin manuscripts. So it was also chanted for the Eucharistic adoration.
The authorship of the hymn by Thomas Aquinas was previously doubted by some scholars. More recent scholarship has put such doubts to rest. Thomas seems to have used it also as a private prayer, for a daily adoration of the Blessed Sacrament.
Adoro te devote is one of the medieval poetic compositions, being used as spoken prayers and also as chanted hymns, which were preserved in the Roman Missal published in 1570 following the Council of Trent (1545–1563).
The hymn is still sung today, though its use is optional in the post-Vatican II ordinary form.
Text and literal translation.
There are two variant readings of the Latin text, with slightly different nuances to some of the words:
""most of the variations occur in the first two verses. The substitution of the words "posset omni scélere" in place of "quit ab omni scélere" in the second-to-last verse and "cupio" for "sitio" in the closing one are practically the only other changes"".
This does not affect the overall meaning of the lines or stanzas so that "either variant may be legitimately used according to local custom."
Poetic English translations.
There have been at least 16 significant English translations of Adoro te devote, reflecting its popularity as a prayer and hymn, including versions by Edward Bouverie Pusey, Edward Caswall, and Gerard Manley Hopkins. One translated version is the popular hymn "Humbly We Adore Thee". The melody is Benedictine plainsong from the 13th century.
Liturgical use.
This hymn was added to the Roman Missal in 1570 by Pope Pius V, and also it has more quotations in the "Catechism of the Catholic Church" (n. 1381). This Eucharistic hymn was generally chanted with a genuflection in front of the Blessed Sacrament.
The hymn is typically used as an Eucharistic hymn and is sung either during the distribution of communion at Mass, or during the Benediction of the Blessed Sacrament.
Final prayer.
Until the first half of the nineteenth century, the (Eucharistic) chant Adoro te devote was often used to be followed by this second Thanksgiving prayer, referred to Jesus Christ God:
The 13 December 1849, Pope Pius IX stated a period of some days of indulgence in favour of any Christian people having declaimed this prayer.