Can a perfectly good and wise God impose “impossible obligations” (takīf bi mā lāyotāq), that is, obligations surpassing human ability? This question holds profound significance within Islamic theology and carries weighty implications in the realm of Islamic law and morality, particularly concerning the comprehension of divine commands. For example, if one concedes that a perfectly good and wise God cannot (or does not) mandate impossible obligations, then an individual may reasonably question the religious validity of any prescription of Sharia if it is demonstrated to exceed human capacity. As I have argued in this paper, one’s position on this matter is tightly connected to the principle of Ultra posse nemo obligatur or “ought implies can” (from now on “the ability principle”). Historically, Muʿtazili, Shīʿī, and Māturīdi scholars have advocated for the ability principle and thus the notion that a perfectly good and wise God cannot issue impossible commands. Many of these scholars argued that the truth of the ability principle is necessary and evident to reason, while they also offered some textual and rational justifications for their position. In recent times, some modernist Shīʿī scholars have leveraged the ability principle and the concept of the immorality of impossible obligations not only as a guiding principle to reform traditional Islamic jurisprudence but also as a cornerstone for the revival of a morally sensitive understanding of religion in general, which they term "humane religion" or Dīn-e Insānī or Dīn-e Rahmānī. Conversely, Ashʿarī scholars have contested this principle and thus asserted that it falls within God’s power and authority to impose obligations beyond human ability. This paper sets out to first analyse different types of “ought” and “can” to identify the most appropriate understandings of these concepts in the context of moral and legal obligations. Second, it explores the traditional Ashʿarī arguments, championed by Abu Hamid Muhammad Ghazali, challenging the ability principle and advocating for the moral permissibility of God's imposition of impossible obligations. Additionally, it delves into traditional Muʿtazili and Shīʿī responses to this notion, as articulated by Qazi Abdul Jabbar and Shaykh Tusi. However, it finally argues that the ability principle (and consequently, its theological and legal implications) faces some new philosophical challenges that warrant careful consideration. There are at least three scenarios that can be counted against the ability principle and its theological and legal implications: First, the phenomenon of psychological compulsion, such as kleptomania. Second, scenarios originally offered by Harry Frankfurt (known as “Frankfurt cases”), and finally, cases in which the moral status of one person’s action depends on some other person’s having a certain moral obligation. This paper briefly examines these new challenges and argues that there are ways to meet them.