What is the proper posture of the people during the Agnus Dei when the people say, “Lamb of God who takes away the sins of the world” (three times). Should we stand or kneel?
Here is a reply from Father Francis Hoffman, J.C.D.:
You should stand during the Agnus Dei. The posture that follows the Agnus Dei depends on your dioceses.
We can find the answer to your question in the 2012 Edition of the General Instruction of the Roman Missal:
“In the dioceses of the United States of America, they should kneel beginning after the singing or recitation of the Sanctus (Holy, Holy, Holy) until after the Amen of the Eucharistic Prayer, except when prevented on occasion by ill health, or for reasons of lack of space, of the large number of people present, or for another reasonable cause. However, those who do not kneel ought to make a profound bow when the Priest genuflects after the Consecration.
“The faithful kneel after the Agnus Dei (Lamb of God) unless the Diocesan Bishop determines otherwise.
“For the sake of uniformity in gestures and bodily postures during one and the same celebration, the faithful should follow the instructions which the Deacon, a lay minister, or the Priest gives, according to what is laid down in the Missal” (No 43).