He is most renowned as the author of the 1648 publication Imagen de la Virgen María, a description and theological interpretation of an apparition to Juan Diego of the Virgin Mary as Our Lady of Guadalupe which is the first published narrative of the event.
The existence of a cult of the Virgin Mary at a chapel (or ermita) at Tepeyac, focussed on a painted cult image of the Virgin and enjoying a reputation for miraculous healing, was certainly established by 1556.
[1] Professor Brading, a scholar of Mexican history, noted of Sánchez: "even if he did not initiate the devotion, he determined the manner in which the image was exalted and justified.
On various occasions he served as chaplain of the chapel of Our Lady of Los Remedios, and in 1662 he joined an archconfraternity of secular priests which was later constituted as the first Oratory of Saint Philip Neri in Mexico.
He was buried at the sanctuary of the Virgin at Guadalupe, having been her lifelong devotee and the first of the "four evangelists" of the Guadalupan apparition.