We have just finished the fast-free week of Pentecost and tomorrow we go back to regular fasting in a big way with the Apostle’s Fast for the next month.
Of course, there is testimony in the New Testament that the Christians continued keeping the Jewish Feast of Pentecost, albeit with new nuances to the meanings of that feast. Tertullian, Origen, and others testify to this continued practice in sub-apostolic times.
The fast-free week following Pentecost is also very ancient and is mentioned in the Apostolic Constitutions of the fourth-century, which is a work compiling ante-Nicene practices of the Christian Church.
It mentions the weeklong celebration of Pentecost by saying, “Therefore, after you have kept the festival of Pentecost, keep one week more festival, and after that fast; for it is reasonable to rejoice for the gift of God, and to fast after that relaxation…”
Of course, by returning to fasting immediately after this week, it is referring to the regular Wednesday and Friday fasts we have kept since the first century as recorded in the Didache (itself written while the New Testament was still being written). It also means the Apostles Fast, as St. Leo the Great explained in 461, “After the long feast of Pentecost, fasting is especially necessary to purify our thoughts and render us worthy to receive the Gifts of the Holy Spirit … Therefore, the salutary custom was established of fasting after the joyful days during which we celebrated the resurrection and ascension of our Lord, and the coming of the Holy Spirit.”
By keeping these practices from the heart, Orthodox Christians have a real historical link to the first Christians, and we know ourselves to be in a Church that transcends time historically and space geographically.
It is an organic unity of the Body of Christ joined in doctrine, practices, church governance, and patterns of worship. So much so that, were you to take an Orthodox Catholic Christian from any of the twenty-one Christian centuries and place him in any other century and culture, he would recognize that Church as his own.
That is part of what we celebrate today on the Feast of All Saints.