When you are brought into union with Christ and into communion with His Church, you will enter into a kind of spiritual marriage. You will be integrated into His faithful Bride, the Church. As physical marital union between a husband and wife is only permissible, pure, and blessed between two who have united together through marriage, sharing in the Holy Mysteries is only permitted, pure, and blessed by those who have entered into union with the Holy Orthodox Church.
In right order, a marriage between a man and woman should be established first, then the benefits of marriage, including physical marital union and having children, are enjoyed. To use the image of the Hospital again, only individuals who first have been admitted to the Hospital under the care of the Physician receive the benefits of being patients, that is, receiving the full medical treatment, including the prescribed Medicines. Therefore, those outside of the Orthodox Church are forbidden from receiving the Holy Mysteries of the Church. They are neither the Bride nor patients in the Hospital. They are not yet ready to enjoy the benefits of the spiritual marriage nor the benefits of a patient by receiving the Medicine. As Adam and Eve, those separated from the Holy Orthodox Church are not yet ready to partake of the fruit of the Tree.
Likewise, Orthodox Christians refuse to participate in the rituals or sacraments of heterodox (non-Orthodox) religious groups that are separated from the Orthodox Church. As a pure Bride, always reject spiritual adultery, instead remaining faithful to Christ and in unity with His Holy Church. The Mystery of the Church holds everything you need for your salvation.
Text copyright © 2018 by Fr. Symeon D. S. Kees