On the fifth day (Friday) of the Fasting of Catechumens, the Armenian Church commemorates the remembrance day of the Prophet Jonah. However it is celebrated not as the feast of the Prophet Jonah, but as the memory of an example of great repentance and abstinence, which Jonah urged.
Prophet Jonah is one of the minor prophets of the Holy Bible. Jonah is the central figure of the Book of Jonah, which details his reluctance in delivering God’s judgement on the city of Nineveh, and then his subsequent, albeit begrudged, return to the divine mission after he is swallowed by a large sea creature. Jonah remained inside the fish for three days and three nights. It was only after Jonah’s prayer and redemption did the Lord allow the fish to free Jonah. This time he obeyed the Lord’s command and went to Nineveh. On the first day, Jonah started into the city. He proclaimed: “Forty more days and Nineveh will be overturned.” The Ninevites believed God. They declared a fast, and all of them, from the greatest to the least, even the king, put on sackcloth. When God saw what they did and how they turned from their evil ways, he had compassion and did not bring upon them the destruction he had threatened.
Later Christ brings the example of the Prophet Jonah to the Pharisees asking for a divine sign:
Then some of the scribes and Pharisees said to him, “Teacher, we wish to see a sign from you.” But he answered them, “An evil and adulterous generation asks for a sign, but no sign will be given to it except the sign of the prophet Jonah. For just as Jonah was three days and three nights in the belly of the sea monster, so for three days and three nights the Son of Man will be in the heart of the earth.”