CAPUT IEIUNII. – Since the seventh century, Ash Wednesday has been known as feria IV in capite ieiunii, because, according to Roman usage, the Lenten fast begins on this day, whereas the First Sunday of Lent retains the ancient name caput quadragesimae, because in ancient times, as still today in the Ambrosian rite, Lent began with this Sunday, of which the Roman Liturgy too preserves valuable traces in its liturgical texts.
According to St. Maximus of Turin (PL 57, 301), some began to prepare themselves for Lent devotioro ieiunio, while others, in order to have forty full days of fasting, added the last four days of the preceding week, at first privately and then officially. The Gelasian Sacramentary already attests to this practice. St. Gregory the Great (Hom. 6 in Evang.) does not yet count them among the Lenten days. The Mozarabic and Gallican liturgies did not originally know them: consequently, no mention is made of Ash Wednesday or of feria IV in capite ieiunii in the Orationale Gothicum, in St. Isidore, in the councils, in the Lectionary of Luxeuil, in the Sacramentary of Bobbio, or in the Missale Gothicum; only in the Missale Mixtum does it appear as a merely external and later addition. It was only in a seventh-century addition to the Gelasian that feria IV Cinerum was designated as c. i., and in the ninth century Amalarius (PL 105, 108) states clearly: «Quarta feria quinquagesimam et quadragesimum ieiunium, quod protenditur in Pascha Domini, inchoamus». In the Roman rite, however, the four days soon became part of Lent, that is, at the time when the other Lenten days acquired their fixed stations and when the antiphons for Communion were composed: in fact, the Communio for Ash Wednesday is taken from the first Psalm. It is known that the Lenten ferias take their Communion antiphons from the Psalms in the order of their numerical sequence. In competition with caput quadragesimae, Wednesday, which became c. i., assumed an increasingly solemn character: on that day public penance began with the exclusion of sinners, whose blessing and imposition of ashes the liturgy still preserves (v.), as well as their fasting, which little by little was extended to all the faithful. Thus, on account of its solemnity, Ash Wednesday became the beginning of the Lenten fast and at the same time of the Lenten season, while the significance of the First Sunday of Lent gradually fell ever further into oblivion in the minds of the people.