St John Gualbert (985 - 1073) was a member of the Florentine nobility.
One Good Friday he was entering Florence accompanied by armed followers, when in a narrow lane he came upon a man who had killed his brother. He was about to kill the man in revenge, when the other fell upon his knees with arms outstretched in the form of a cross and begged for mercy in the name of Christ, who had been crucified on that day. John forgave him. He entered the Benedictine Church at San Miniato to pray, and the figure on the crucifix bowed its head to him in recognition of his generosity.
He became a Benedictine monk at San Miniato, but unwilling to compromise in the fight against simony, of which both his abbot and bishop were guilty, he left and settled at Vallombrosa, where he founded his monastery.
The Congregation he founded was united with the Slyvestrines by 1680.