|Book of Kells folio 27v|
This page was used in a ceremony for new believers known as the "Opening of the Ears" (Apertio Aurium).
As new believers prepared for baptism they went through basic catechesis. During Lent catechumens were brought into the church for a reading of the first few verses from each of the four gospels, with an explanation of the four symbolic figures for the Evangelists (Man, Lion, Ox, Eagle). See here for more on the background to these symbols.
Ó Carragáin has suggested that pages like folio 27v in the Book of Kells were displayed at the altar and the four-fold Gospel explained. This ceremony was a visual presentation of the Gospel to an illiterate audience preparing to join the church. This ceremony was part of the broader preparation of catechumens for their upcoming Easter baptism.
The earliest account of the details of the Apertio Aurium ceremony are given by Bede (672-735), who notes in his allegorical commentary on the Tabernacle,
"There are four pillars at the entrance of the court [of the Tabernacle] because no one is able to come into the unity of the holy church except through the faith and the sacraments of the gospel, which are contained in four books. For this reason, in that same church the pleasing custom has developed from ancient times that the beginnings of the four gospels are recited to those who are about to be catechized and initiated into the Christian sacraments, and at the opening of their ears they are carefully instructed concerning the figures [of the evangelists] and their order, so that from then on they may know and remember which books, and how many, [contain] the words by which they ought chiefly to be instructed in the true faith."
Another brief reference by Bede is given in his commentary on Ezra-Nehemiah,
"…not through our own freedom of will but through the illumination of divine light that, after hearing the prophetic worlds of the Gospels, we are incorporated into the members of the Holy Church. And a beautiful and wholesome custom has developed in the church through the teaching of the Fathers that the mystery of the four Gospels is explained and their beginnings are recited to those who are being catechized."
The Book of Kells, and other Insular illuminated manuscripts, were not merely intended as objects of aesthetic beauty, but also as a means of teaching and instructing people in the faith of the Christian Gospel.
Éamonn Ó Carragáin, “Traditio Evangeliorum and Sustentatio: The Relevance of Liturgical Ceremonies to the Book of Kells,” in The Book of Kells: Proceedings of a Conference at Trinity College, Dublin, 6-9 September 1992, edited by Felicity O’Mahony (Dublin: Scholar Press, 1994), 400-401.
Bede, On the Tabernacle, translated by Arthur G. Holder (Liverpool: Liverpool University Press, 1994), 101.