Ash Wednesday is the first day of Lent in the Christian tradition and is marked by the placement of ash on the faithful's foreheads during service.
Many of the modern church practices today have roots in ancient practices and traditions – and one of them is the donning of ash.
Ashes are a significant symbol in Biblical narratives. One such story was the pronouncement of Nineveh as a 'wicked city' by the prophet Jonah. The king of Nineveh, who became repentant of what had become of his city, wore sackcloth and sat on a pile of ashes. God saw the act of penitence and was moved to spare the wicked city, who had been guilty of worshipping false idols and gods.
Another story related to ashes can be found in the Gospel of Matthew. In the narrative, Jesus deplores the conditions of the poor and the marginalized as he passed through several towns.
He became angry at religious leaders who continually taught righteousness to believers but were living in laps of luxury. He called the religious leaders 'whitewashed tombs' that looked beautiful outside but were full of filth from within. Jesus mentioned the sackcloth and ashes once again as a form of sincere penitence.
The use of ashes in the church was recorded as far back as the ninth century. Placing ashes on the body was considered a sign of genuine penitence for one's sins.
The placement of the ashes was done in church as it was a public demonstration of one's faith as well. The formal ritualization of ash came about in 1901 under Pope Urban II. It was Pope Urban II who institutionalized the act as the beginning of the 40 days of Lent, at a time when people had been trying to imitate the Jesus' 40 days of fasting.