The Russian Orthodox Church requires anyone who desires to receive Holy Communion prepare themselves with confession, the Pre-Communion Prayer Rule, and to abstain from food or drink from midnight on. Most of the world's Local Orthodox Churches hold to this standard, recognizing that the clergy, as guardians of the Mysteries, must make sure anyone who approaches the chalice is Orthodox, and is properly prepared.
The Church's requirement that one must be a member of the Orthodox Church before approaching the chalice relates to the fact that communion is the outward expression of having all things in common, both in faith and worship, since receiving the Holy Mysteries is the fruit of unity. The sacrament of Holy Communion does not create unity as some heretics opine, but it is the result of a unity of faith that already exists.
In receiving Holy Communion, we are eating and drinking the very Body and Blood of the Savior for the healing of body and soul. This is not simply the remembrance of a past event, but the very participation of the Heavenly Banquet. We enter into a place where there is neither time nor space, and participate in this eternal banquet for the transformation of our very being.
Since the Eucharist is a true participation and foretaste of heavenly things, it is imperative that we be properly prepared, for to eat and drink unworthily is to put our immortal soul at risk.
Orthodoxy in North America does not have a common practice in regards to preparation for receiving the Eucharist. Some jurisdictions allow members to approach the chalice without having confessed, thus contributing to the abuse of the Mysteries. Yet on the flip side, those who are required to confess before communing can fall into the habit of going through the motions of confession without giving the priest adequate time to offer spiritual direction. When this happens, confession is sometimes no different than refraining from confession, for we can easily run through the usual litany of sins, get absolution, and start the week off without having made a heartfelt confession at all.
If we have made a good confession we must have a plan of action that will allow the Holy Spirit to transform our heart, for true repentance MUST include a commitment to go and sin no more! This requires the guidance of a confessor and takes more time than simply getting in a long line prior to the service. For this reason it is best to make your confession ahead of time rather than to wait until Sunday morning before the liturgy begins.
The midnight fast that must precede the Divine Liturgy, together with the Pre-Communion Prayer Rule, is an additionally important step in our proper preparation for receiving the Eucharist, for these become the tools by which we make the reality of what we are receiving something more than mere ritual. If we were simply reenacting or commemorating the last meal the Lord shared with His disciples, confession, fasting, and preparatory prayers would be unnecessary. The requirements the Church places on her faithful is clear evidence that the Lord did not say, this is "like'' my body and blood, rather He said, “This is My Body … This is My Blood”. The Eucharist is no mere symbol, it is, in fact the ultimate reality of our eternal life. Come therefore and receive this great gift of our Lord, this promise of His Kingdom which is to come – and prepare so that these Mysteries may not to be to your condemnation, but to the healing of your soul and body.