Baring-Gould’s sources: At Sienna on the Saturday before Passion Sunday; but by the Dominican Order on March 22nd; the Roman Martyrology on March 20th, the day of his death. He was beatified by Gregory XV. His Acts were written by friars Gisberti, Recuperato di Petromala, Aldobrandini Paparoni, and Olvado, by order of Honorius IV., the then reigning pope, from documents transmitted to them within a month of the decease of S. Ambrose. These originals also exist, and have been printed along with the Acts by the Bollandists.

S. Ambrose [bishop of Milan (d. 397)] was of the family of the Sansedoni, on his father's side, and of the Stribelini on that of his mother, both illustrious in Sienna. He was deformed at his birth, his legs and feet being twisted, but as his nurse was hearing mass one holy-day, in the church of the Dominicans, and was praying before some holy relics [the bodily remains of a saint, or objects they used, kept with honor], afterwards exposed to the veneration of the faithful, the child suddenly pronounced the name of Jesus thrice, and lost at the same moment every trace of deformity.

As he grew up, his play was connected with holy things. Till he was seven, he amused himself with carving little crosses, making little oratories, imitating with other children the processions and psalmody of the Church. When he grew older, he obtained his father's consent to his lodging pilgrims. He furnished for the purpose a room in the house, and went to the gate of the city every Saturday to bring home with him the first five pilgrims whom he encountered. He then washed their feet, and ministered in every way to their comforts. On the morrow he went with them to mass, and guided them about the town to all the places of devotion. Every Sunday evening after vespers he visited the hospital, and every Friday the prison. He continued these holy exercises till he was seventeen, when he entered the Dominican order. He made his full profession next year, in 1238, and was then sent to Paris and to Cologne to prosecute his studies. At Cologne he became the pupil of Albertus Magnus, along with the great S. Thomas Aquinas. When his education was complete, he taught theology in Paris for two years, and then preached in France, Germany, and Italy. The people of Sienna having taken part with Mansfeld, the bastard of Frederick II., who was in hostility with the pope, were placed under an interdict. Ambrose undertook to reconcile them with the Holy See, and was so successful, that the Siennese have chosen him, on account of this eminent service rendered them, as the patron of their city.

During the forty-nine years of his monastic life, he maintained the utmost self-discipline. He never slept more than four hours every night. After matins he remained for two hours in prayer in the choir, and spent the rest of the night in study till prime. He preached with singular fire and action. In the Lent [the forty days of fasting before Easter] of 1286, he broke a blood-vessel as he was preaching, and was obliged to leave the pulpit. The hæmorrhage ceasing next day, he insisted on resuming his sermon, but the vessel burst again, and he lost so much blood that he felt his hour was at hand. He made his general confession, and having received the last sacraments, breathed forth his pure soul in the sixty-sixth year of his age, on March 20th, 1286.