Posted by QUAERITUR: My uncle wants to become Catholic and ive been taking him to RCIA classes. The priest is a great guy but said you can receive the Eucharist if you intend to confess after mass. I know this is bogus since you’re still in mortal sin. How and with what source(s) should I let the priest know?
ASK FATHER: If I’m aware of mortal sin, can I receive Communion if I intend to go to confession later? | Fr. Z’s Blog
Among other sources, look at the Catechism of the Catholic Church and can. 916 of the 1983 Code of Canon Law.
Can. 916 A person who is conscious of grave sin is not to celebrate Mass or receive the body of the Lord without previous sacramental confession unless there is a grave reason and there is no opportunity to confess; in this case the person is to remember the obligation to make an act of perfect contrition which includes the resolution of confessing as soon as possible.
Unless there is a GRAVE REASON.
“It’s Sunday, I’m here, and I want to receive!”, is NOT a GRAVE REASON.
People are not obliged to receive Communion at every Mass. So many sacrilegious Communions could be avoided if people could get this into their heads. Rather… if priests would do their jobs correctly?
Also, even though there are not many places now – sadly – where confessions are heard before and during Mass, they are nevertheless usually heard some place nearby in the days before Sunday or Holy Days of Obligation. Since a person ought to be making a daily examination of conscience, this scenario can be avoided with relative ease.
Of course there are rare situations where circumstances are different. That is why the canon is written as it is.
Bottom line: If a person is aware of mortal sin, and is sure about it, he must not receive until after he has made a good confession of all mortal sins in kind and number and has received absolution.
This is not hard.