Q. When, if ever, is it appropriate, permitted, or required to have three readings at mass, outside of Sundays and Solemnities?
I ask because, for the Masses for Various Needs and Occasions and for the Ritual Masses, it’s not really clear to me when (if ever) three readings should be used. I see they all have options from the Old Testament and New Testament, but I don’t know whether three readings are intended to be used at those masses, or whether there are simply options from both the Old and New Testaments but only 2 readings should be used (one of which being the Gospel). I’m also unclear whether this means 3 readings are supposed to be used, or if 2 readings only in those masses are acceptable.
The documents, as far as I can tell, don’t really state it clearly. For example, para. 79 in the General Introduction to the Lectionary says “In Masses to which three readings are assigned, all three are to be used,” but I don’t know whether 3 options in the Lectionary itself is an indication that three readings are “assigned”, or whether those are simply the permissible options for a mass with 2 readings. The only masses for which I find a clear, unambiguous assignment of 3 readings are masses on Sundays and Solemnities. But even then, if a Mass for Various Needs is celebrated on a Sunday, is it a “Sunday Mass”?
A. As you surmise, three readings are expected at Sundays and solemnities but not at other times. All those readings appear in masses for various needs and occasions in order to give options, but on a weekday only one reading should be selected before the gospel. In the rare instance when the bishop requests one of those masses be celebrated on an Ordinary Time Sunday, then you would use 3 readings. Ritual masses allow three readings but do not require them. You should find directions in the front material for each liturgical book, such as the forthcoming Order for Celebrating Matrimony, paragraphs 55 and 90.