Mediator Dei §90

⁹⁰ First of all the more extrinsic explanations are these: it frequently happens that the faithful assisting at Mass join their prayers alternately with those of the priest, and sometimes - a more frequent occurrence in ancient times - they offer to the ministers at the altar bread and wine to be changed into the body and blood of Christ, and, finally, by their alms they get the priest to offer the divine victim for their intentions.