Question: Which one of the eight most ancient Christian Hymns requires the first letter to be capitalized?

Context paragraphs:
Lex orandi, lex credendi: Lex orandi, lex credendi (Latin loosely translated as "the law of praying [is] the law of believing") is a motto in Christian tradition, which means that it is prayer which leads to belief, or that it is liturgy which leads to theology.  It refers to the relationship between worship and belief, and is an ancient Christian principle which provided a measure for developing the ancient Christian creeds, the canon of scripture and other doctrinal matters based on the prayer texts of the Church, that is, the Church's liturgy.  In the Early Church, there was liturgical tradition before there was a common creed and before there was an officially sanctioned biblical canon.  These liturgical traditions provided the theological framework for establishing the creeds and canon.

PascalCase: In programming, PascalCase is the practice of writing compound words or phrases such that the first letter of each concatenated word is capitalized.  No other characters are used to separate the words, like hyphens or underscores.

The New Century Hymnal: The New Century Hymnal is a comprehensive hymnal and worship book published in 1995 for the United Church of Christ.  The hymnal contains a wide-variety of traditional Christian hymns and worship songs, many contemporary hymns and songs (typically in traditional idioms, though), a substantial selection of "world music" selections (hymns and worship songs from non-European-American) origin, a full lectionary-based Psalter, service music selections, and a selection of liturgies from the UCC Book of Worship (1986).  Generally speaking, the hymnal is theologically within the "mainline" Protestant tradition, with a slant toward liturgical forms.

A Dictionary of Hymnology: A Dictionary of Hymnology: Origin and History of Christian Hymns and Hymnwriters of All Ages and Nations, Together with Biographical and Critical Notices of Their Authors and Translators by John D. Julian, first published in 1892, is a standard historical reference for early Christian hymns, with more than 40,000 entries.

Abecedarius: An abecedarius is an acrostic in which the first letter of every word, strophe or verse follows the order of the alphabet.  Abecedarius is also a generic term for an alphabet book, which dates back to Biblical writings such as the Psalms, which used successive letters of the Hebrew alphabet as the first letter of each stanza.  Another example is Old Polish poem "Skarga umierającego" ("A Dying Man Complaint").  Such poems are important historical sources for development of orthography.  They can be proofs that some letters were used long ago and later were totally forgotten.  Bishop Constantine of Preslav's abecedarius (shown on the right) from 9th century documents the early Slavic alphabet.  Nowadays abecedariuses are written chiefly for children.

Christian Science Hymnal: The Christian Science Hymnal is a collection of hymns sanctioned for use in Christian Science services including Sunday services and Wednesday evening testimony meetings, as well as in occasional informal hymn sings.  It includes both traditional Christian hymns, traditional hymns with minor adaptations better suiting Christian Science theology, and hymns unique to Christian Science, including seven poems by the denomination's founder Mary Baker Eddy set to various tunes: "Christ, My Refuge", "Christmas Morn", "Communion Hymn", "Feed My Sheep", "Love", "Mother's Evening Prayer", and "Satisfied".  Found in the Supplement section are the hymns, "I Need Thee Every Hour", "I'm a Pilgrim and I'm a Stranger", and "Eternity", which were originally included in the Hymnal in accordance with [Mrs. Eddy's] wish."

Rosary: The Rosary (pronunciation: /ˈrəʊz(ə)ri/, Latin: "rosarium " , in the sense of "crown of roses" or "garland of roses"), usually in the form of the Dominican Rosary, is a form of prayer used especially in the Catholic Church named for the string of knots or beads used to count the component prayers.  When used of the form of prayer, the word is usually capitalized ("the Rosary"), as is customary for other names of prayers, such as "the Lord's Prayer", "the Hail Mary", "the Magnificat".  When referring to the beads, it is normally written with a lower-case initial ("a rosary").

Magnificat: The Magnificat (Latin: [My soul] magnifies [the Lord] ) is a canticle, also known as the Song of Mary, the Canticle of Mary, and, in the Byzantine tradition, the Ode of the Theotokos (Greek: Ἡ ᾨδὴ τῆς Θεοτόκου ).  It is traditionally incorporated into the liturgical services of the Catholic Church (at vespers) and of the Eastern Orthodox churches (at the morning services).  It is one of the eight most ancient Christian hymns and perhaps the earliest Marian hymn.  Its name comes from the incipit of the Latin version of the canticle's text.

Josiah Ransome-Kuti: Josiah Jesse Ransome-Kuti (June 1, 1855 – September 4, 1930) was a Nigerian clergyman and music composer.  He was known for setting Christian hymns to indigenous music, and for writing Christian hymns in Yoruba.

Symbol (chemistry): In relation to the chemical elements, a symbol is a code for a chemical element.  Many functional groups has their own chemical symbol, e.g. Ph for the phenyl group, and Me for the methyl group.  Chemical symbols for elements normally consist of one or two letters from the Latin alphabet, but can contain three when the element has a systematic temporary name (as of March 2017, no discovered elements have such a name), and are written with the first letter capitalized.

Supporting paragraphs: Rosary Magnificat
Answer: The Magnificat