St. John Cassian (d. 435AD) was a disciple of St. John Chrysostom and wrote extensively about the monastic life. His comments on fasting and keeping Lenten periods are very instructive as the received Tradition which he taught was not as fixed and rule bound as are some current ideas in Orthodoxy. He did not know of one set of ascetic rules which applied to all monks, let alone all lay people. Fasting was to be kept by a common discipline known in the local community, but these rules were not to be applied to guests and visitors, and in fact were not to be discussed with those outside of the local community. He writes:
“…They also declared that the common discipline of fasting should not casually be disclosed to anyone but should, as far as possible, be hidden and concealed. They were of the opinion, rather, that if some brothers paid a visit it was better to practice the virtue of hospitality and love than to display the strictness of our abstinence and the daily rigor of our chosen orientation […] And fasting, as beneficial and necessary as it may be, is nonetheless a gift that is voluntarily offered, whereas the requirements of the commandment demand that the work of love be carried out. And so I welcome Christ in you and must refresh him.” (The Institutes, pp 132-133)
For St. John Cassian, fasting, as important and essential as it might be to monks, was voluntary offering, not to be done in fulfillment of some rule or duty. On the other hand, practicing hospitality was clearly taught and commanded by the Lord Jesus Christ. The virtue of hospitality and love outranked the virtue of strict fasting. Christ commanded us to love, He gave no direct commandment to fast. To practice hospitality and charity with others is what Christ demanded of us. To share a meal with family, a visitor or a stranger is to fulfill the Gospel commandments to love one another. His teachings are very much in line with the kind of fasting approved by God in Isaiah 58 and with Christ’s teaching about the Last Judgment Matthew 25.