By law in Peru, descendants of Africans and of native Americans were barred from becoming full members of religious orders. The only route open to Martin was to ask the Dominicans of Holy Rosary Priory in Lima to accept him as a donado, a volunteer who performed menial tasks in the monastery in return for the privilege of wearing the habit and living with the religious community.
At the age of 15, Martin asked to be admitted to the Dominican Priority, in Lima. He was accepted first as a servant boy. As his duties grew, he was promoted to almoner.
Martin continued to practice his old trades of barbering and healing, and was said to have performed many miraculous cures. He also took on kitchen work, laundry, and cleaning. After eight years at Holy Rosary Priority, the prior Juan de Lorenzana, decided to turn a blind eye to the law and permit Martin to take his vows as a member of the Third Order of Saint Dominic.