After leaving school, Thomas went to the nearby city of Zwolle to visit his brother again, after Johann had become the prior of the Monastery of Mount St. Agnes there. This community was one of the canons regular of the Congregation of Windesheim, founded by disciples of Groote in order to provide a way of life more in keeping with the norms of monastic life of the period. Thomas himself entered Mount St. Agnes in 1406. He was not ordained a priest, however, until almost a decade later. He became a prolific copyist and writer. Thomas received Holy Orders in 1413 and was made sub-prior of the monastery in 1429.