Ash Wednesday marks the beginning of the 40-day Lent fast observed by many Christian sects around the world and is typically associated with the ashes some worshippers wear on their foreheads throughout the day. The ritual of applying ashes in church is meant to signify internal penance and the need to be redeemed by God’s mercy, according to the Vatican.

While the ashes are one of the most eye-catching aspects of the observance, Ash Wednesday is about more than the symbolism of ashes and heralds the beginning of a holy season of fasting and repentance leading up to Easter. Below are some important facts about the holy day and its observance:

The ashes used to mark observer’s foreheads in Church typically come from burned palm trees that are typically incinerated during the previous year’s Palm Sunday celebrations.

When applying the ashes, the priest typically recites one or both of the following, according to the Latin Times: “Remember that thou art dust, and to dust thou shalt return.” Genesis 3:19, and “Repent, and believe the Gospel.” Mark 1:15

While it is most common in the U.S. to see ashes made into the shape of a cross, there is no set rule on applying the ashes and methods can vary based on local custom, the National Catholic Register said. It’s common to see priests use holy water to turn the ashes into a sort of paste in English-speaking countries, where the ashes are usually applied into the shape of a cross. Whereas in parts of Italy, Spain and Latin America, sprinkling dry ashes on the crown of the head is also commonly seen.

There is actually no biblical commandment mandating the observance of Ash Wednesday however, the ashes as a form of repentance feature prominently in the Bible, where the importance of fasting and self examination are also highly emphasized.

While Eastern Orthodox Christians also observe a 40-day fast, theirs begins on a different day, known as Clean Monday, and thus many do not participate in Ash Wednesday observances.

Ash Wednesday is not a holy day of obligation but, as the start of one of the holiest seasons in the Christian liturgical calendar, it is nonetheless a significant holy day when fasting is highly encouraged.

The rite was not directly connected to the beginning of Lent historically. "This custom is an ancient penitential practice common among the Hebrew people," Father Lukasz Wisniewski, vice-rector of the Redemptoris Mater Archdiocesan Missionary Seminary in Massachusetts, the Boston Pilot reported. The priest pointed to the use of ashes to demonstrate repentance in several instances cited in the Hebrew Bible, including in the book of Jonah.