Q: Our parish formerly knelt after the Lamb of God. Recently our priest told us we should not. I know that it’s not in the rubrics to kneel, but would it be sinful to do so?
A: Although it is a custom in many parishes to kneel following the Lamb of God, the rubrics actually mandate the reverse. The General Instruction to the Roman Missal mandates standing after the conclusion of the Great Amen through the rest of Mass. A special dispensation has not been made for America in this regard, so actually, we do have an obligation to stand following the Lamb of God.
If it would cause a greater pastoral problem if one were to stand (for example, if one were the only person standing in the entire congregation), then kneeling might be appropriate. However, if your pastor is trying to bring the parish into conformity with the Church’s liturgical laws then you should thank and praise God for it (you’re one of the lucky ones!) and do everything you can to assist him, even if your personal devotional preferences would be otherwise.
My own personal preferences would be to kneel after the Lamb of God. However, this cannot be justified on legal grounds, and if my parish priest wishes to encourage greater conformity to liturgical law, I will ignore my personal preference and do what the Church says. To do otherwise would be disobedience to the priest and the Church in a matter over which they have jurisdiction (how liturgy is to be celebrated — though a priest only has jurisdiction in this area when he does not go against the Church’s liturgical laws). The analog would be for a child to disobey a parent in an area over which the parent has jurisdiction, and that would that be sinful.
What I would do if I were you would be to go to the priest and say, “Father, I’m glad we have begun to celebrate the liturgy according to the Church’s laws in this area; now let’s bring our celebration into line in these other areas as well… 😀