From Saint Wiki
Communion (Eucharistic) (the receiving of the Blessed Eucharist). The receiving of Communion is obligatory for all members of Christ's Church who have attained an age when they fully possess the requisite qualifications alluded to in the fourth commandment of the Church to "receive communion annually, at Easter or thereabouts." Wilful disregard of this commandment is a mortal sin. It was our Lord Himself who established communion as a means necessary for our salvation, when he said: "Except you eat the flesh of the Son of Man, and drink his blood, you shall not have life in you" (John vi. 54). Communion is obligatory on members of the Church who have attained the age of twelve years, according to St. Alphonsus; though they may be admitted earlier, and as soon as they can "discern the body of our Lord," that is, are capable of understanding the importance and solemnity of the act, and of appreciating the requisite dispositions of respect and humility with which all should approach the Blessed Sacrament. "Whosoever shall eat this bread, or drink the chalice of the Lord unworthily, shall be guilty of the body and the blood of the Lord" (I. Cor. xi. 27, 28, 29). Therefore, "let a man prove himself, and so let him eat of that bread."
Our Lord Jesus Christ said: "Unless you eat the flesh of the Son of Man and drink His blood, you shall not have life in you" (John vi. 54). Therefore, we can scarcely accomplish this divine precept unless by receiving holy Communion at least once a year; and, indeed, how can we expect to be received by our Saviour into the eternal happiness of heaven, if we give ourselves so little trouble to receive Him here on earth, and with Him, His promise and pledge of that everlasting life? The partaking of the holy communion at Easter is an obligation inseparable from the commemoration of the institution of the most Blessed Sacrament by our Lord Jesus Christ; and to impress us with a vivid remembrance of our Saviour's passion and death, of which the Holy Eucharist is the perpetual and living memorial, according to Christ's own words as given to us by St. Paul: "As often as you shall eat this bread, and drink the chalice, you shall show the death of the Lord, until He come" (I. Cor. xi. 26). It is desirable, but not obligatory, that the Easter Communion should be received in the Church of the parish to which we belong, for, by doing this, we can offer good example, one to another; we strengthen the union that should exist between ourselves and the minister of Christ under whose supervision we are placed, by public acknowledgment of his authority; and enable him to recognize those who have acquitted themselves of their duty, that he may strive to bring defaulters to repentance.
As the Holy Eucharist is a sacrament of the living, the necessary dispositions for rightly receiving communion, consist in being in a state of grace, that is, conscious of being entirely free from mortal sin. Otherwise we should commit a sacrilege, and expose ourselves to severe spiritual and temporal physical punishments. For, according to the words of St. Paul: "Whosoever shall eat this bread, or drink the chalice of the Lord, unworthily, shall be guilty of the body and blood of the Lord . . . For he that eateth and drinketh unworthily, eateth and drinketh judgment to himself, not discerning the body of the Lord" (I. Cor. xi. 27, 29). Dispositions not strictly obligatory, but nevertheless most expedient, are the purifying of the soul from venial sins with a strong desire to avoid falling into temptation, and the making serious effort to correct ourselves of faults displeasing to God, and to adorn our souls with holy thoughts, firm resolves of good, and the meritorious actions performed in the strength of faith, the confidence of hope, the generous love of charity, as well as other virtues springing from these three theological virtues. As to the requisite dispositions of our bodies, it is absolutely essential that we should be fasting from midnight, scrupulously avoiding anything whatsoever to eat or drink, either by intention or inadvertence; leaving no possible chance of violating the precept, not to swallow any substance that has entered the mouth from without. Our outward behavior should be such as is suitable, and should be eminently consistent with reserve, propriety, modesty, and purity, both in our attire and deportment. We should approach the altar-rail with the utmost gravity of demeanor, receiving the Holy Host from the hand of the priest, without unnecessary contact with the lips or teeth, and retiring, without precipitation, to quiet meditation, adoration, and other prayer, in which we should spend some length of time, say, a quarter of an hour. For what moment can be so propititious for the supplications we have to make, and for offering grateful recognition of the favors we have received, as when we are, temporarily, the living tabernacle of our Lord Jesus Christ? We should express to Him the worship and gratitude of our whole hearts, imploring aid for our own spiritual and temporal needs, for those of the living and the dead who share our prayers, and for all the Faithful of Holy Church; making good resolutions for our future conduct, and asking help of grace in the accomplishment of our desires and resolves. It is furthermore well to keep, throughout the day, a devout remembrance of the inestimable favor received, and even a pious recollection of our First Communion.