From a reader:
I am a Seminarian who is in a parish which has a “Vigil Mass of Sunday” on Saturday evenings. I have read your posts regarding receiving communion twice in one day, and I know the “Vigil” Mass legally fulfills ones obligation. My question is; does this mean I can’t receive communion on Saturday night and the two Sunday Masses (I sometimes have to serve all three)? Would it be a mortal sin?
No, all things being equal it is not a mortal sin. Yes, the law permits that you receive Holy Communion on Saturday evening and then twice on Sunday.
Reception of Communion and fulfilling your Sunday obligation are different issues. You fulfill your obligation by participating, attending Holy Mass. You are not obliged to receive Communion at every Mass. As a matter of fact, if you know you are not in the state of grace, you should not receive Communion.
Back to the issue of the number of times you may receive in a 24 hour period.
The 1983 Code of Canon Law says:
Can. 917 – Qui sanctissimam Eucharistiam iam recepit, potest eam iterum eadem die suscipere solummodo intra eucharisticam celebrationem cui participat, salvo praescripto Can. 921, § 2. … Someone who has already received the Most Holy Eucharist can receive it again (iterum) on the same day only within the Eucharistic celebration [i.e. Mass] in which the person participates, with due regard for the prescription of can. 921 § 2.
Remember: iterum does not mean “again and again”, but merely “again one more time”.
Also, that “Eucharistic celebration” in the canon does not mean just any service involving Communion. It means Mass. That was cleared up by the Holy See in an official response to a dubium.
Can. 921 § 2 says that if a person is in danger of death, he may receive Communion even it is not in the context of Mass. That is Viaticum.
Saturday ends at midnight. At midnight Sunday begins. You can receive even twice on Saturday and then twice on Sunday.
Work out with your spiritual director whether or not you want to receive three times in such a short time span.