Yūsuf serves as a model of virtue and wisdom in pietistic literature. He is extolled in Ṣūfī manuals such as that of Abū Naṣr al-Sarrād̲j̲'s K. al-Lumaʿ as a paragon of forgiveness. "He also epitomizes the chastity that is based on complete trust in God, for it was his absolute piety that prompted God to personally intervene to prevent him from the transgression of succumbing to sexual temptation." He is an archetype of wisdom and faith, although arguably still human (as is shown in his interactions with his brothers when in Egypt). As has been noted, commentary never fails to mention Yūsuf's beauty—a strong theme in post-Ḳurʾānic literature. Firestone notes, "His beauty was so exceptional that the behavior of the wife of al-ʿAzīz is forgiven, or at least mitigated, because of the unavoidably uncontrollable love and passion that his countenance would rouse in her. Such portrayals are found in many genres of Islamic literatures, but are most famous in Nūr al-Dīn ʿAbd al-Raḥmān Dijāmī's [q.v.] Yūsuf wa Zulayk̲h̲ā, which incorporates many of the motifs and attributes associated with his beauty in earlier works."