He built the monastery of Santa Maria del Berrogal, and was the chief founder of the Custody of San Gabriel, for which he visited Rome.
In 1523, when he was 50, he was chosen to head a band of twelve Franciscans who were to work for the conversion of the Mexican natives, in what is sometimes called the "spiritual conquest.
However, the friar's presence also complicated the ruler's life, since Fray Martín pressured him to give up his multiple wives, a practice incompatible with Christianity.
Fray Martín was returned to Tlalmanalco, where the ruler there was also concerned that the friar not die there, and attempted to send him by boat or canoe to Mexico City.
[11][12][13] Fray Martin and his eleven fellow Franciscans, the Twelve Apostles of Mexico baptized large numbers of Indians.