“This is to be a lasting ordinance for you: On the tenth day of the seventh month you must deny yourselves and not do any work–whether native-born or an alien living among you – because on this day atonement will be made for you, to cleanse you. Then, before the Lord, you will be clean from all your sins. It is a sabbath of rest, and you must deny yourselves . . . This is to be a lasting ordinance for you: Atonement is to be made once a year for all the sins of the Israelites.” And it was done, as the Lord commanded Moses. [Leviticus 16:29-34 NIV]
When fasting in accordance with religious doctrine, we observe the rites and methodology prescribed by our creed. Theological systems and their liturgical ceremonies offer rules and regulations that facilitate our acts of worship. Our rabbis, priests, gurus and imams guide us in observing the fast as a community of believer following a divine law.
However, no religion can claim a patent or copyright on worship. Belief, prayer, supplication, repentance, charity, compassion and morality are not the invention or possession of any one religion. Likewise, no religion can claim authorship of fasting.
Fasting is a universal institution whose origin is ensconced in the nature of human beings. We interpret and implement the practice in various ways.
Be cautious that fasting does not become a rust-covered ecclesiastical observance. We do not fast for Yum Kippur, for Lent, or for Ramadan. It is God who imposed the fast, not the religious organizations.
Religions cannot encompass God. Doctrines and canons do not delineate His domain. Our fast is only for God.
Now it has been stated above that fasting is useful as atoning for and preventing sin, and as raising the mind to spiritual things. And everyone is bound by the natural dictate of reason to practice fasting as far as it is necessary for these purposes. Wherefore fasting in general is a matter of precept of the natural law, while the fixing of the time and manner of fasting as becoming and profitable to the Christian people, is a matter of precept of positive law established by ecclesiastical authority: the latter is the Church fast, the former is the fast prescribed by nature. [Thomas Aquinas, Summa Theologica].