On his return home he begged his father's leave to continue the pious exercises he had begun, and retired to a little hermitage not far from Faucon, with a view of living at a distance from the world, united to God alone. But finding his solitude interrupted by the frequent visits of his friends, he desired his father's consent to go to Paris to study divinity, and this he easily obtained. He accomplished his studies with extraordinary success, and received the degree of doctor of divinity with uncommon applause. He was soon after ordained priest, and said his first mass in the chapel of the bishop of Paris, at which the bishop himself, Maurice de Sully, the abbots of S. Victor and of S. Geneviève, and the rector of the university, assisted; admiring the graces of heaven in him, which appeared in his extraordinary devotion on this occasion, as well as at his ordination.
On the day he said his first mass, by a special inspiration from God, he resolved to devote himself to the ransoming of Christian slaves from captivity. But before he entered upon so important a work, he thought it needful to spend some time in retirement, prayer, and mortification. And having heard of a holy hermit, S. Felix of Valois, living in a great wood near Grandlieu, in the diocese of Meaux, he repaired to him, and begged he would admit him into his solitude. Felix soon discovered him to be no novice, and would not treat him as a disciple, but as a companion.
One day, as they were sitting together on the bank of a spring, John disclosed to Felix the design he had formed on the day on which he said his first Mass, of succouring the Christians under Mahomedan slavery, and spoke so movingly upon the subject, that Felix was convinced the design was from God, and offered to assist him in carrying it into execution. They took some time to recommend it to God by prayer and fasting, and then set out for Rome in the midst of a severe winter, towards the end of the year 1197, to obtain the Pope's benediction. They found Innocent III. promoted to the chair of St. Peter, and he being already informed of their sanctity and charitable design by letters of recommendation from the Bishop of Paris, received them as two angels from heaven; lodged them in his own palace, and gave them many long private audiences. After which he assembled the cardinals and some bishops in the palace of S. John Lateran, and asked their advice. After their deliberations he ordered a fast and special prayers, to ascertain the will of heaven. At length, being convinced that these two holy men were led by the Spirit of God, and that great advantage would accrue to the Church from such an institute, he consented to their erecting a new religious order, and declared S. John the first general minister. The Bishop of Paris, and the abbot of S. Victor, were ordered to draw up the rules, which the Pope approved by a bull, in 1198. He ordered the religious to wear a white habit, with a red and blue cross on the breast, and to take the name of the Order of the Holy Trinity. He confirmed it some time after, adding new privileges by a second bull, in 1209.