Today, Ash Wednesday marks the beginning of Lent—40 days of prayer, fasting, and penance—the Church’s remembrance of Jesus' 40 days in the desert before He began His public ministry. All members of the Church (including non-Catholics) are encouraged to receive the ashen cross on their forehead symbolizing our mortality and as a reminder of our identity in Christ we receive in baptism:
Abraham spoke up again: “See how I am presuming to speak to my Lord, though I am but dust and ashes!” (Gen 18:27)
Then I looked and there was the Lamb standing on Mount Zion, and with him a hundred and forty-four thousand who had his name and his Father’s name written on their foreheads. (Rev 14:1)
Revelation can be a very difficult book to interpret because of it’s apocalyptic style. In this verse, some might interpret the “a hundred and forty-four thousand” to be an exact number. When Revelation was written, a thousand meant an innumerable amount. Villages probably seldom had more than a few hundred people, so a crowd of a thousand would’ve been a very big deal. The number twelve in scripture is a reference to the twelve tribes of Israel. In this case, 144 implies twelve “sub-tribes” for every tribe, each with too many people to be counted. An easy way to remember and visualize the number and quantity is the 12th Man. :-)
The passage also describes the name of each person and the name of the Father on their foreheads. Each person’s name has two “parts”. First, our name was officially given to us at Baptism, hence an indelible mark that becomes our identity in Christ; second, we are of this world, mortal, dust. The second name, the Father’s name, is an identity for God—the cross. Thus an ashen cross is a physical representation of what Rev 14:1 describes.
For even more information, check out this post from St. Mary’s Aggie Catholic Blog.