Russian Orthodox Church Protection of Mother of God
Russian Orthodox Church • Patriarchial Parishes in Canada

“This summer fast, which we now call the Apostles fast, was earlier called the fast of Pentecost.

“After the extended feast of Pentecost, the fast is particularly needed in order to cleanse our mind by ascetic labors, and to make us worthy of the gifts of the Holy Spirit,” writes St. Leo the Great. “After the present feast, which the Holy Spirit has sanctified by His descent, all the people usually keep a fast beneficially established for the healing of soul and body, and therefore requiring that we spend it with the appropriate reverence. For we do not doubt that after the Apostles’ hearts were filled with the Spirit of truth promised to them from on high, amongst the other mystical heavenly teachings given by their Teacher, they were given also the teaching on spiritual continence, so that their hearts, purified by fasting, would be made capable of receiving gifts of grace… It is would not be possible to struggle in a pampered body and fattened flesh against the persecutions, and the fierce threats of the ungodly that lay ahead; for that which delights our outer man destroys our inner man, and the more a wise soul mortifies its flesh, the purer it becomes. … In the Apostolic canons inspired by God Himself, the Church fathers have, at the inspiration of the Holy Spirit, established first and foremost that all virtuous labors begin with fasting.”

Blessed Simeon of Thessalonika writes that the fast was established in honor of the Apostles, because we have been vouchsafed many blessings through them, and they have been shown to us as doers and teachers of fasting, obedience… and temperance. “

Source: https://orthochristian.com/47148.html