While the Brown Scapular is a traditional Catholic sacramental, and the reasons for wearing it has been given by Della, I have always regarded it as having it’s Scriptural roots in Deuteronomy
Chapter 6: 6-8
*"Take to heart these words which I enjoin on you today.
Drill them into your children. Speak of them at home and abroad, whether you are busy or at rest.
Bind them at your wrist as a sign and let them be as a pendant on your forehead."*
Also, in Numbers 15:37-40, we are told:
*"The LORD said to Moses,
"Speak to the Israelites and tell them that they and their descendants must put tassels on the corners of their garments, fastening each corner tassel with a violet cord.
When you use these tassels, let the sight of them remind you to keep all the commandments of the LORD, without going wantonly astray after the desires of your hearts and eyes.
Thus you will remember to keep all my commandments and be holy to your God."*
For me, the Scapular is not a free ticket to Heaven. Every day i am reminded by wearing it of the commitment (promises) I have freely made where I offer my day, and everything it contains both good and bad; as an offering to Almighty God, in reparation for my sins and those of the whole world, for the salvation of sinners, and to practise Chastity according to my status in life.
For a Catholic, choosing to wear the Brown Scapular is like enlisting in an army and wearing the uniform of a particular battalian. We are informing Satan that we are Christians who are serving under the banner of Mary in order to win souls for Christ, her beloved Son.
If you like, the scapular makes those who choose to wear it, and not everyone does, particular targets of the Enemy. I mean, those of us who wear a scapular are outawardly identifying ourselves as followers of Christ.
In Catholic Tradition, Mary is the Woman of Genesis (3:15 “I will put enmity between you and the woman, and between your offspring and hers; He will strike at your head, while you strike at his heel.”) and the Woman of Revelation 12.
For the last reference, Catholic Answers catholic.com/thisrock/1997/9705chap.asp can say it better than I.
For myself, I do not believe that I can wear the Scapular, live a sinful life and still get a free ticket to Heaven (or, a get-out-of Hell-free card).