Why must the priest celebrant receive Communion first at Mass, before everyone else? My pastor said that if it’s not done that way, then “it’s not a sacrament.” What do you suppose he meant by that? Christ is still truly present, is he not?
The priest receives first because his reception of Communion completes the sacrificial nature of the Mass. The consecrated host and the precious blood symbolize Christ’s death (i.e., the separation of body and blood). Brought together again in the priest’s reception of the elements, they symbolize Christ’s Resurrection.
Not only is the priest’s reception of the eucharistic body and blood critical to a proper celebration of the liturgy, but it is also true that the congregation’s reception of Communion is not strictly necessary. A priest can celebrate Mass without a congregation (according to the rules in place that govern private Masses), but a congregation cannot have a Mass without a priest.
That said, your priest’s implication that a valid Consecration is dependent on the priest’s reception of Communion is incorrect. The sacrament is confected by a valid Consecration, not by priestly reception of the eucharistic elements.