When Catholics attend Mass on Ash Wednesday, we are marked with a cross on our foreheads using ashes. Why?
Ash Wednesday is the kick-off to the season of Lent. Lent is 40 days (not counting Sundays) before Easter and is our time of preparation so we may be more ready to accept our risen Lord Jesus Christ. Lent is a time of prayer, fasting, sacrifice, but mostly repentance. Lent is a time for us to grow in awareness of our sinfulness and our desperate need for a savior.
What does this have to do with ashes? Let's look to the Bible to see what significance ashes may have considering a theme of repentance.
O daughter of my people, gird on sackcloth, roll in the ashes. Mourn as for an only child with bitter wailing, For sudden upon us comes the destroyer. (Jer 6:26)
I turned to the Lord God, pleading in earnest prayer, with fasting, sackcloth and ashes... (Dn 9:3)
When the news reached the king of Nineveh, he rose from his throne, laid aside his robe, covered himself with sackcloth, and sat in the ashes (Jon 3:6)
Ashes in Old Testament times were a sign of repentance. Why? One reason is that they're uncomfortable and reflect our willingness to pay a price for our sins (same with sackcloth, which is like wearing clothes made of burlap). Another reason is the reminder we hear when we receive the ashes "Remember you are dust and to dust you shall return". Lent is a time to remember our fragile lives do not last forever and we are called to constant repentance for we know not the hour or the day the Lord is coming.
This reminder is even more significant since the ashes we use come from the brunt palm branches blessed and used at the previous years' Palm Sunday celebration. On Palm Sunday we remember the crowds laying palms before Jesus, they cheered for him, they celebrated him, they wanted him to be king.
Less than a week later they called for his death by torture.
The ashes of the palms call us to remember how our praises have turned into a rejection of Christ in our own lives, and to remember that we will soon be called home to him.