ChapterIII-VI. Readings from Sacred Scripture
Reading of Sacred Scripture in General
140. The reading of sacred Scripture, which, following an ancient tradition, takes
place publicly in the liturgy, is to have special importance for all Christians, not
only in the celebration of the eucharist but also in the divine office. The reason is
that this reading is not the result of individual choice or devotion but is the planned decision of the Church itself, in order that in the course of the year the Bride of Christ may unfold the mystery of Christ "from his incarnation and birth until his ascension, the day of Pentecost, and the expectation of blessed hope and of the Lord's return."  In addition, the reading of sacred Scripture in the liturgical celebration is always accompanied by prayer in order that the reading may have greater effect and that, in turn, prayer - especially the praying of the psalms - may gain fuller understanding and become more fervent and devout because of the reading.
141. In the liturgy of the hours there is a longer reading of sacred Scripture and a shorter reading.
142. The longer reading, optional at morning prayer and evening prayer, is described in no. 46.
Cycle of Scripture Readings in the Office of Readings
143. The cycle of readings from sacred Scripture in the office of readings takes into account both those special seasons during which by an ancient tradition particular books are to be read and the cycle of readings at Mass. The liturgy of the hours is thus coordinated with the Mass in such a way that the scriptural readings in the office complement the readings at Mass and so provide a complete view of the history of salvation.
144. Without prejudice to the exception noted in no. 73, there are no readings from the Gospel in the liturgy of the hours, since in the Mass each year the Gospel is read in its entirety.
145. There are two cycles of biblical readings. The first is a one-year cycle and is incorporated into The Liturgy of the Hours; the second, given in the supplement for optional use, is a two-year cycle, like the cycle of readings at weekday Masses in Ordinary Time.
146. The two-year cycle of readings for the liturgy of the hours is so arranged that each year there are readings from nearly all the books of sacred Scripture as well as longer and more difficult texts that are not suitable for inclusion in the Mass. The New Testament as a whole is read each year, partly in the Mass, partly in the liturgy of the hours; but for the Old Testament books a selection has been made of those parts that are of greater importance for the understanding of the history of salvation and for deepening devotion.
The complementarity between the readings in the liturgy of the hours and in the Mass in no way assigns the same texts to the same days or spreads the same books over the same seasons. This would leave the liturgy of the hours with the less important passages and upset the sequence of texts. Rather this complementarity necessarily demands that the same book be used in the Mass and in the liturgy of the hours in alternate years or that, if it is read in the same year, there be some interval in between.
147. During Advent, following an ancient tradition, passages are read from Isaiah in a semicontinuous sequence, alternating in a two-year cycle. In addition, the Book of Ruth and certain prophecies from Micah are read. Since there are special readings from 17 to 24 December (both dates included), readings for the Third Week of Advent which fall on these dates are omitted.
148. From 29 December until 5 January the readings for Year I are taken from the Letter to the Colossians (which considers the incarnation of the Lord within the context of the whole history of salvation) and the readings for Year II are taken from the Song of Songs (which foreshadows the union of God and humanity in Christ): "God the Father prepared a wedding feast for God his Son when he united him with human nature in the womb of the Virgin, when he who is God before all ages willed that his Son should become man at the end of the ages. 
149. From 7 January until the Saturday after the Epiphany the readings are eschatological texts from Isaiah 60-66 and Baruch. Readings remaining unused are omitted for that year.
150. During Lent the readings for the first year are passages from Deuteronomy and the Letter to the Hebrews. Those for the second year review the history of salvation from Exodus, Leviticus, and Numbers. The Letter to the Hebrews interprets the Old Covenant in the light of the paschal mystery of Christ. A passage from the same letter, on Christ's sacrifice (Heb 9:11-28), is read on Good Friday; another, on the Lord's rest (Heb 4:1-16), is read on Holy Saturday. On the other days of Holy Week the readings in Year I are the third and fourth Songs of the Servant of the Lord and extracts from Lamentations; in Year II the prophet Jeremiah is read, as a type of Christ in his passion.
151. During the Easter season, apart from the First and Second Sundays of Easter and the solemnities of the Ascension and Pentecost, there are the traditional readings from the First Letter of Peter, the Book of Revelation, and the Letters of John (for Year 1), and from the Acts of the Apostles (for Year II).
152. From the Monday after the feast of the Baptism of the Lord until Lent and from the Monday after Pentecost until Advent there is a continuous series of thirty-four weeks in Ordinary Time.
This series is interrupted from Ash Wednesday until Pentecost. On the Monday after Pentecost Sunday the cycle of readings in Ordinary Time is resumed, beginning with the week after the one interrupted because of Lent; the reading assigned to the Sunday is omitted.
In years with only thirty-three weeks in Ordinary Time, the week immediately following Pentecost is dropped, in order to retain the readings of the last weeks which are eschatological readings.
The books of the Old Testament are arranged so as to follow the history of salvation: God reveals himself in the history of his people as he leads and enlightens them in progressive stages. This is why prophetic books are read along with the historical books, but with due consideration of the period in which the prophets lived and taught. Hence, the cycle of readings from the Old Testament contains, in Year 1, the historical books and prophetic utterances from the Book of Joshua as far as, and including, the time of the exile. In Year II, after the readings from Genesis (read before Lent), the history of salvation is resumed after the exile up to the time of the Maccabees. Year 11 includes the later prophets, the wisdom literature, and the narratives in Esther, Tobit, and Judith.
The letters of the apostles not read at special times are distributed through the year in a way that takes into account the readings at Mass and the chronological order in which these letters were written.
153. The one-year cycle is shortened in such a way that each year special passages from sacred Scripture are read, but in correlation with the two-year cycle of readings at Mass, to which it is intended to be complementary.
154. Proper readings are assigned for solemnities and feasts; otherwise the readings are taken from the respective Common of Saints.
155. As far as possible, each passage read keeps to a certain unity. In order therefore to strike a balance in length (otherwise difficult to achieve in view of the different literary genres of the books), some verses are occasionally omitted, though omissions are always noted. But it is permissible and commendable to read the complete passage from an approved text.
156. The short readings or "chapters" (capitula) are referred to in no. 45, which describes their importance in the liturgy of the hours. They have been chosen to give clear and concise expression to a theme or an exhortation. Care has also been taken to ensure variety.
157. Accordingly, four weekly series of short readings have been composed for Ordinary Time. They are incorporated into the psalter in such a way that the reading changes during the four weeks. There are also weekly series for the seasons of Advent, Christmas, Lent, and Easter, In addition there are proper short readings for solemnities, feasts, and some memorials, as well as a one-week series for night prayer.
158. The following determined the choice of short readings:
- in accordance with tradition, exclusion of the Gospels;
- respect for the special character of Sunday, or even of Friday, and of the individual hours;
- use only of the New Testament for the readings at evening prayer, following as they do a New Testament canticle.