Ash Wednesday

Ash Wednesday is a day usually celebrated in Catholicism which takes place about 40 days before Easter, marking it as the beginning of the season called Lent, where followers of the faith would fast until Easter. On the day of Ash Wednesday, a special Mass would be celebrated where the people would be marked with a black ash mark on their foreheads as a reminder that, like the first man Adam, they came from dust and to dust they shall return.

Empath: The Luckiest Smurf stories
In the EMPATH: The Luckiest Smurf story series, Ash Wednesday is mostly celebrated among humans. A similar day called Redemption Day is observed by the Smurfs, in which their successful swim across the Pool Of Souls would be rewarded by a black ash mark on their foreheads as a reminder that their innocence would be guarded for another year.