Due to the activity of Canon Rudolf of Worms, monasteries of penances, self-established in Western and Central Europe, were in 1227 joined into a new order in the Church: Ordo sanctae Mariae Magdalenae de Poenitentia. Initially, the nuns followed the Benedictine rule in the Cistercian version. However, due to the specificity of the calling, it was necessary to change the law. Pope Gregory IX did this in 1232, thus giving the nuns the so-called rule of St Augustine and the constitutions of the Dominican nuns (the so-called Rule of Saint Sixtus). Although a copy of the original bull of Gregory IX has not been found, Hubertus Ermisch published its text with the Rule of St Sixtus in the Document Collection of the City of Friborg in Saxony in Leipzig in 1883. Besides, the papal bull with the text of The Rule of St Sixtus is known from the Bullarium Ordinis Praedicatorum (ed. by Antonio Bremond Romae, 1729). The oldest document containing the Rule of St Sixtus is kept at the State Archives in Wrocław, in the set of files Naumburg a. Queis. We present a Polish translation of the preserved text of the rule from the Nowogrodziec Monastery. It remains the common heritage of both Magdalene sisters and Dominican nuns.