121 Now it is very fitting, as the liturgy otherwise lays down, that the people receive holy communion after the priest has partaken of the divine repast upon the altar; and, as we have written above, they should be commended who, when present at Mass, receive hosts consecrated at the same Mass, so that it is actually verified, "that as many of us, as, at this altar, shall partake of and receive the most holy body and blood of thy Son, may be filled with every heavenly blessing and grace."
Source: Mediator Dei (Vatican.va)