Q: Someone wants to replace the first reading for Sunday Mass with a non-biblical reading (words of the founder of the religious community that founded the school). That’s not allowed, right?
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A: Correct. But that doesn’t mean some groups don’t do it. However, GIRM 31 lets a priest give an introduction to the Liturgy of the Word before the first reading. There’s a scripted example of this at the Easter Vigil. I think a reading from the founder of the community after the collect intending to frame the scripture readings that follow would give the proper balance between a treasured text in the community and the unequalled Word of God.