The tradition of abstinence from food throughout the day or even several days goes back to the time of the Old Testament. Such fast could be imposed on the entire Israeli people on the eve of important events, before military battles or in relation to some disasters.That is how Moses fasted on Mount Sinai.
In the liturgical circle of the Orthodox Church there are also days when believers can abstain from food throughout the day.This is Good Friday, Exaltation of the Holy Cross, Christmas Eve, Epiphany Eve. In Greece, there is a tradition of not eating anything during the first three days of Lent, that is, before the first Presanctified Liturgy. And many believers adhere to this rule.
However, for most people, such abstinence is unbearable, therefore the Church has never accepted this pious tradition as a norm mandatory for all believers. In the Orthodox Church, emphasis is placed on the quality of fast, and not on its quantity. Abstinence in food is an important element of fast, but not the only one. The attitude to fast in Orthodoxy is complex, integral and includes not only the rejection of meat, eggs and milk, but also from evil deeds, evil thoughts. Nevertheless, if someone has the strength and desire to refuse food for the whole day, this can be done with the blessing of the spiritual father.
Translated by The Catalogue of Good Deeds