This article delves into the life of Riyāh ibn Amr al-Kaysī who was a notable figure of the ascetic period, exploring his biography, ascetic philosophy, the allegations surrounding him, and his relationships with Rābia al-Adawiyya. The lifestyles and ideas of the ascetics living during the ascetic period have formed the foundation of sufi thought. However, some ascetics have also been subject to criticism. One such criticized ascetic is Riyāh ibn Amr al-Kaysī, who lived in Basra during the 2nd century AH (Hijri). Riyāh faced accusations of heresy from both Abū Dāvūd al-Sicistānī and Abū al-Huseyn al-Malatī. According to Malatī, Riyāh contended that, having reached the state of divine intimacy through love for Allah, he was not bound by the legal obligations of Sharia. Additionally, recent researchers have posited the possibility that Riyāh might have been married to Rābia al-Adawiyya. The aim of this study is to thoroughly examine the ascetic philosophy of Riyāh ibn Amr al-Kaysī, the accusations against him, and his relationship with Rābia al-Adawiyya. The study begins by presenting information about Riyāh's life, the ascetic environment in which he lived, and his ascetic philosophy. Subsequently, the accusations against him are scrutinized in light of these details. The research findings indicate that Riyāh did not lead a life distant from religious beliefs; on the contrary, he adhered to a rigorous ascetic lifestyle. Consequently, he faced accusations of heresy, and it is narrated that he attained martyrdom in Yakapınar, Adana.