The Lectionary contains all the readings for Mass, for the two year cycle for daily readings, and the three year cycle for Sunday readings.
There are 3 Readings at Sunday Mass. The 1st is Old Testament and the 2nd and 3rd is from the New Testament. -- RJ, R.E.
Roman Catholic AnswerThe entire Mass from the introductory greeting to the dismissal is taken from the Bible. In addition to the fixed parts of the Mass - entirely taken from the Bible, the first half of the Mass, the Liturgy of the Word, is based on the Jewish service and is built around three lengthy readings from the Bible, with a Psalm between the first two - usually the Old Testament, and the New Testament (other than the Gospels), followed by a Gospel reading. The readings for Sunday Mass are on a three year cycle and the readings for weekday Mass on are a two year cycle. At the end of the cycle you will have read nearly the entire Bible, certainly from every book in the Bible.
If you attend a wedding Mass or a sacramental Mass on Saturday, it DOES NOT fulfill the Sunday Mass obligation. To fulfill a Sunday or Holy Day obligation, a Mass on the previous day (the Vigil) must start at 4 pm or later and use the appropriate readings for that Sunday or Holy Day. Some Dioceses will allow variations (for example, different readings at a Sunday Confirmation Mass).
If it is a regularly scheduled Sunday Mass at the time and place appointed by the Bishop, then the readings must be of the Sunday. If the Bishop or priest is having a later Mass just for the RCIA, then they may use any readings approved by the Bishop, check with your local Chancery.
Called "cycles" of the liturgical year, these rotate to a new letter (A, B or C) each calendar year at the First Sunday in Advent. Each years cycle has different readings from the Bible.
During a Sunday service or a Sunday mass, any reading can be taken from the books in the bible, from the book of Genesis to the book of revelation.And usually the sermon is based on these readings.
The Gospel readings for year A are mostly taken from St. Matthew, the other readings are from all over the Bible to highlight the Gospel.
Catholic AnswerDifferent dioceses may have different regulations on when an anticipated Sunday or Holy Day Mass may be celebrated on the day before. It must be late Afternoon or evening, a Saturday Mass celebrated with the weekday (Saturday) readings does NOT count as your Sunday obligation. The important thing is whether the actual Mass being said is the Mass of Sunday or the Holy Day: i.e., it has three readings from the Sunday, the Gloria, Creed, etc. If the Sunday Mass is being celebrated, then it fulfills your obligation. If it is another Mass, say, perhaps a Saturday Mass being celebrated in the afternoon for a wedding, then it would not count for your obligation. If you have a particular question about a particular situation, please ask the priest who will be saying the Mass.
The Creed (Apostle or Nicene)
The readings are already picked out by the Church. They change every 3 years on Sunday (A,B,C) and are always the same. On weekdays, they are on a two year cycle (I,II).
On all Sundays and Solemnities (Christmas, All Saints, Immaculate Conception, Assumption, etc.) there are three (well, four if you count the psalm), usually an Old Testament reading, a psalm, a New Testament reading, and the Gospel. Weekday Masses only have one reading, the psalm, and the Gospel, there is no second reading on a non-solemnity.