The Apostles, following the example of Jesus Christ, fasted twice forty days each, namely from the day of Pentecost and the days before the feast of Epiphany (Denha). But, as to how this fast originated in the Church is not exactly known. One could say that since Christ has said to the apostles that ‘the sons of the bride chamber cannot  fast as long as the bridegroom is with them, but days shall come when the bridegroom will be taken from them and then they shall fast’ (Lk 5:34-35). Thus, after the ascension of Jesus Christ and after the day of Pentecost, the apostles began to keep this fast and gradually it was adopted as a custom in the Church. At present, in the Malankara Church, this fast is reduced into 13 days corresponding to the number of 12 apostles and St.Paul (June 16-29). This fast is observed in order to become aware of the responsibility of the faithful in the Church and missionary activities. : From Mosc.in