Gregory IX, Pope. [Letter to Agnes of Prague, 1234 (2)] in Bullarium Franciscanum Romanorum Pontificum 1.134-35

[Letter from Pope Gregory IX to Agnes of Prague]
Two months after she had entered the monastery, the pope praises Agnes for having chosen the life of a poor Clare over marriage to a powerful ruler. The monastery and hospital referred to were built by Agnes, but her brother finally supported her choice of life.
Online at Epistolae (See also Bibliographia record).