Today we commemorate a king who was a faithful disciple of Christ Crucified, and whose life bears witness to the truth that virtue is not always rewarded in this world. Louis was inspired by his zeal for the Faith to attempt the reconquest of the Holy Places sanctified by the blood of the Redeemer, but instead of triumph and victory, he only met with defeat and captivity, and when he was at last ransomed by his people, he brought back to Paris as a symbolic trophy of his campaigns the crown of thorns once worn by Our Savior.
He died of plague under the walls of Tunis, to which city he was about to lay siege, on August 25, 1270. Christian Rome dedicated a celebrated church to him, not far from the Stadium Domitiani.
The custom of genuflecting at the words in the Credo, et homo factus est, and of making profound reverence at the passage in the Gospels recording the death of Jesus was introduced by this pious king in his own chapel; they are now part of the ordinary ceremonial.
(Source: The New Roman Missal, Rev. F. X. Lasance)