Catechism:
The Sunday Eucharist is the foundation and confirmation of all Christian practice. For this reason the faithful are obliged to participate in the Eucharist on days of obligation, unless excused for a serious reason (for example, illness, the care of infants) or dispensed by their own pastor.119 Those who deliberately fail in this obligation commit a grave sin.
Does this mean that if you do not recieve Communion, you commit a serious sin/have not fulfilled your obligation? What if you forgot to fast?
Thanks!
Being at mass is participating (celebrating) in the Eucharist. Which is a command in scripture, especially on the DAY, the Lord’s Day, Sunday. Obviously, Catholics should also be in a state of grace and receive what is being celebrated.
From The Church and scripture
Heb 10: 23 Let us hold fast the confession of our hope without wavering, for he who promised is faithful; 24 and let us consider how to stir up one another to love and good works, 25 not neglecting to meet together, as is the habit of some, but encouraging one another, and all the more as you see the Day drawing near. 26 For if we sin deliberately after receiving the knowledge of the truth, there no longer remains a sacrifice for sins, 27 but a fearful prospect of judgment, and a fury of fire which will consume the adversaries. 28 A man who has violated the law of Moses dies without mercy at the testimony of two or three witnesses. 29 How much worse punishment do you think will be deserved by the man who has spurned the Son of God and profaned the blood of the covenant by which he was sanctified, and outraged the Spirit of grace? 30 For we know him who said, “Vengeance is mine, I will repay.” And again, “The Lord will judge his people.” 31 It is a fearful thing to fall into the hands of the living God."
Unpacking that
deliberate Failure to meet on the Day, is already a huge sin “the Day” = the LORD’S DAY / Sunday/ the Day Our Lord Resurrected (v 25)
when they meet what are they doing? They are offering the “sacrifice for sin”, (v 26 ) & “blood of the covenant”( v 29) = the words Our Lord spoke instituting the Eucharist Matthew 26:28 Mark 14:24 They are celebrating the Mass, the Eucharist
Therefore, those who deliberately fail to celebrate the Eucharist on Sunday after being given the knowledge of truth, (v 25 - 26) ◦ there no longer remains, a sacrifice for sin and blood of the covenant for THEM ( v 26) a fearful prospect of judgement awaits Them (v 27) ◦ and a fury of fire will consume these adversaries (v 27) ◦ They Spurn the Son of God (v 29) ◦ They outrage the spirit of grace (v 29) Re: that sin, Based on those consequences described,
Thus
Mass on Sunday is a command, not a suggestion . To deliberately miss Mass on Sunday (given those consequences described) is a (grave) mortal sin. Dying in that is disastrous.