Of God and His Creatures

The deniers of the Objective Presence deny that there is any sacramental union where, owing to sin, there is no spiritual union. According to them, Christ is not except where He is received with faith and love; and an unworthy Communion is no Communion at all. In the theology of the Catholic Church, the one Sacrament which is invalidated by an illicit reception is the Sacrament of Penance, of which the acts of the penitent are a constituent part.

Of God and His Creatures: 4.74