The Black Scapular of the Passion of Our Lord Jesus Christ is distinguished from other Scapulars in this way: It is made of black cloth, having on the front the figure of a Heart surmounted by a White Cross. In the centre of the Heart are the letters: JESU .. XPI .. PASSIO .. meaning: “The Passion of Jesus Christ.” Beneath these letters are three nails. They represent the nails that pierced the Hands and Feet of Jesus.
On the second half of the Scapular is a picture of Jesus on the Cross. On the two halves of the Scapular, in each corner, appear a Chalice, a Veil with Christ’s Face imprinted on it, a Crown of Thorns, and a stone Column to which Christ was bound and beaten with whips. On the lower part of each half of the Scapular there appears this Latin sentence: “Sit Semper in Cordibus Nostris.” This means: “May it [Christ’s Passion] be always in our hearts.”
The Scapular represents, in a small size, the habit in which St. Paul of the Cross, Founder of the Passionists, saw himself clothed during a vision. This vision was bestowed upon him during the time he was cherishing the design of founding a new Congregation, to be devoted in a special manner to the sufferings and death of Jesus.
Article (pdf) Our Scapular, Passionist Magazine 1949