According to St. Bernard of Clairvaux, he asked Jesus which was His greatest unrecorded suffering and the wound that inflicted the most pain on Him in Calvary, and Jesus answered:
“I HAD ON MY SHOULDER, WHILE I BORE MY CROSS ON THE WAY OF SORROWS, A GRIEVOUS WOUND WHICH WAS MORE PAINFUL THAN THE OTHERS AND WHICH IS NOT RECORDED BY MEN. HONOR THIS WOUND WITH THY DEVOTION AND I WILL GRANT THEE WHATSOEVER THOU DOST ASK THROUGH ITS VIRTUE AND MERIT AND IN REGARD TO ALL THOSE WHO SHALL VENERATE THIS WOUND, I WILL REMIT TO THEM ALL THEIR VENIAL SINS AND WILL NO LONGER REMEMBER THEIR MORTAL SINS.”
In the twelfth century Pope Eugenius III approved of the promises with regards to this prayer. The modern version of the prayer bears the imprimatur of Bishop Thomas D. Bevan.
"O Loving Jesus, meek Lamb of God, I a miserable sinner, salute and worship the most Sacred Wound of Thy Shoulder on which Thou didst bear Thy heavy Cross, which so tore Thy flesh and laid bare Thy Bones as to inflict on Thee an anguish greater than any other wound of Thy Most Blessed Body. I adore Thee, O Jesus most sorrowful; I praise and glorify Thee, and give Thee thanks for this most sacred and painful Wound, beseeching Thee by that exceeding pain, and by the crushing burden of Thy heavy Cross to be merciful to me, a sinner, to forgive me all my mortal and venial sins, and to lead me on towards Heaven along the Way of the Cross. Amen."