In 1238 St. Louis was profoundly shocked by the news that the crown of thorns was a forfeited pledge at Venice for an unpaid loan advanced by some Venetian merchants to the Emperor Baldwin of Constantinople. He paid the debt,[52] redeemed the pledge, and secured the relic for Paris. The king met his envoys at Sens, and barefooted, himself carried the sacred treasure enclosed in three caskets, one of wood, one of silver and one of gold, to Paris. The procession took eight days to reach the city, and so great were the multitudes who thronged to see it, that a large platform was raised in a field outside the walls, from which several prelates exposed it in turn to the veneration of the people. Thence it was taken to the cathedral of Notre Dame, the king dressed in a simple tunic, and barefoot, still carrying the relic. From the cathedral it was transferred to the royal chapel of St. Nicholas within the precincts of the palace. A year later the Emperor Baldwin was constrained to part with other relics, including a piece of the true cross, the blade of the lance and the sponge of the Passion. To enshrine them and the crown of thorns the chapel of St. Nicholas was demolished and the beautiful Sainte Chapelle built in its place. The upper chapel was dedicated to the relics; the lower to the Blessed Virgin, and on solemn festivals the king would himself expose the relics to the people. St. Louis was zealous in his devotion and for a time attended matins in the new chapel at midnight, until, suffering much headache in consequence, he was persuaded to have the office celebrated in the early morning before prime. His piety, however, was by no means austere: he had all the French gaiety of heart, dearly loved a good story, and was excellent company at table, where he loved to sit conversing with Robert de Sorbon, his chaplain. "It is a bad thing," he said one day to Joinville, "to take another man's goods, because _rendre_ (to restore) is so difficult, that even to pronounce the word makes the tongue sore by reason of the r's in it."
[Footnote 52: By a subtle irony, part of the money was derived from the tribute of the Jews of Paris.]
At another time they were talking of the duties of a layman towards Jews and Infidels. "Let me tell you a story," said St. Louis. "The monks of Cluny once arranged a great conference between some learned clerks and Jews. When the conference opened, an old knight who for love of Christ was given bread and shelter at the monastery, approached the abbot and begged leave to say the first word. The abbot, after some protest against the irregularity, was persuaded to grant permission, and the knight, leaning on his stick, requested that the greatest scholar and rabbi among the Jews might be brought before him. 'Master,' said the knight, 'do you believe that the Blessed Virgin Mary gave birth to Jesus and held Him at her breast, and that she is the Virgin Mother of God?' The Jew answered that he believed it not at all. 'Then,' said the knight, 'fool that thou art to have entered God's house and His church, and thou shalt rue it,' Thereupon he lifted his stick, smote the rabbi under the ear and felled him to the ground. The terrified Jews fled, carrying their master with them, and so," said St. Louis, "ended the conference. And I tell you, let none but a great clerk dispute; the business of a layman when he hears the Christian religion defamed is to defend it with his sharp sword and thrust his weapon into the miscreant's body as far as it will go."