There are two kinds of worship: Individual and Communal
(a) In prayer, for example, there is individual prayer; you pray in your room to your Fr. who sees in secret. This does not cancel the existence of communal prayer for all the groups of believers to pray in one spirit, in one soul and in one voice. Examples of such prayers are numerous in the New Testament. One of these examples is the prayer of the believers after the release of Peter and John from prison: "So when they heard that, they raised their voice to God with one accord and said…" (Acts 4:24).Of course the Lord’s commandment regarding praying in secret (Matt.6:6) does not apply to such prayer.
(b) Likewise in charity, there is a charitable deed done in secret as an individual act in which you do not let your left hand know what your right hand is doing (Matt.6:3). But this does not cancel the general charity collected from everyone, as when King David collected donations to build the Temple. He mentioned in detail how much he contributed, and how much was contributed by the leaders of the fathers’ houses, the leaders of the tribes of Israel, the captains of thousands and of hundreds, and the officers over the king’s work (IChr.29:3-9). Another example is when the rich people put their gifts in the Temple treasury and the poor widow put in two very small copper coins (Lk.21:1,2).
(c) Likewise in fasting, there is individual fasting practiced in secret which does not cancel the general fast shared by the whole community of believers.
Biblical Examples of Communal Fasting
There are numerous examples of communal fasts in the Holy Bible, such as:
(a) The people’s fast at the time of Esther:
All the people fasted together at the same time for one purpose, praying for one request from the Lord, and the Lord accepted their fast and granted them their request (Esth.4).
(b) The fast of the people of Nineveh:They all fasted together and not in secret, and the Lord accepted their fast and forgave them their sins (Jon.3).
(c) The people’s fast at the time of Nehemiah and Ezra:Nehemiah says: "Now on the twenty-fourth day of this month the children of Israel were assembled with fasting, in sackcloth, and with dust on their heads" (Neh.9:1). And Ezra says: " Then I proclaimed a fast there at the river of Ahava, that we might humble ourselves before our God, to seek from Him the right way for us and our little ones and all our possessions" (Ezra 8:21).
(d) The fast at the time of Joel:The Bible says: "Now, therefore,’ says the Lord, ‘Turn to Me with all your heart, with fasting, with weeping, and with mourning.’ ….consecrate a fast, call a sacred assembly; gather the people, sanctify the congregation, assemble the elders, gather the children and nursing babes; let the bridegroom go out from his chamber, and the bride from her dressing room" (Joel 2:12-17).
(e) The Apostles’ fast in the New Testament:When the Lord Jesus Christ was asked why His disciples did not fast, He replied: "But the days will come when the bridegroom will be taken away from them, and then they will fast (Matt.9:15). The Apostles did fast together and not in secret, and the Lord accepted their fast.Some examples of the Apostles’ fasts: "As they ministered to the Lord and fasted, the Holy Spirit said, "Now separate to Me Barnabas and Saul for the work to which I have called them. Then, having fasted and prayed, and laid hands on them…." (Acts 13:2,3).
(f) St. Paul fasted for a long time together with all the people on the ship (Acts 27:21).
Therefore communal fasting is acceptable and is a Biblical doctrine. It is proof of the oneness of soul in worship and in approaching God, especially if the purpose of the fast is a matter which concerns the whole community, or if the whole community partakes in the fast, as they do in prayer, in one soul.