Al-Mahdi in the context of "Harun al-Rashid"

Ilm al-kalam or ilm al-lahut, often shortened to kalam, is the scholastic, speculative, or rational study of Islamic theology (aqida). It can also be defined as the science that studies the fundamental doctrines of Islamic faith (usul al-din), proving their validity, or refuting doubts regarding them rationally via logic. Kalām was born out of the need to establish and defend the tenets of Islam against philosophical doubters and non-Muslims, and also to defend against heretical and religious innovations (bidʿah). A scholar of kalam is referred to as a mutakallim (plural mutakallimun), a role distinguished from those of Islamic philosophers and jurists.

After its first beginnings in the late Umayyad period, the Kalām experienced its rise in the early Abbasid period, when the Caliph al-Mahdi commissioned Mutakallimūn to write books against the followers of Iranian religions, and the Barmakid vizier Yahya ibn Khalid held Kalām discussions with members of various religions and confessional groups in his house. By the 10th century, the Muʿtazilites were main pioneers of 'Kalam' during the early formative period of Islam. However, due to increased criticism by traditionalist Muslim scholars that the Mu'tazilites started departing from mainstream Sunni orthodoxy, they were refuted heavily. Soon after, two new important Sunni Kalām schools emerged: the Ashʿaris and the Maturidis. They positioned themselves against the growing Neoplatonic and Aristotelian philosophy within the Mu'tazilites and elevated the "Kalām science" (ʿilm al-kalām) as an acceptable ranking science in mainstream Sunni discourse. Some of the arguments of these Mutakallimūn also found their way into Jewish and Christian theological discussions in the Middle Ages. Kalām science by the early modern period was essentially limited to the study of manuals and commentaries, from the late 19th century onwards various reform thinkers appeared in British India and the Ottoman Empire who called for the founding of a "new Kalām".

Abū Muḥammad Mūsā ibn al-Mahdī al-Hādī (Arabic: أبو محمد موسى بن المهدي الهادي; 26 April 764 CE  – 14 September 786 CE) better known by his laqab al-Hādī (الهادي‎) was the fourth Abbasid caliph who succeeded his father al-Mahdi and ruled from 169 AH (785 CE) until his death in 170 AH (786 CE). His short reign ended with internal chaos and power struggles with his mother.

Al-Aqsa (/æl ˈæksə/; Arabic: الأَقْصَى, romanized: Al-Aqṣā) or al-Masjid al-Aqṣā (Arabic: المسجد الأقصى) is the compound of Islamic religious buildings that sit atop the Temple Mount, also known as the Haram al-Sharif, in the Old City of Jerusalem, including the Dome of the Rock, many mosques and prayer halls, madrasas, zawiyas, khalwas and other domes and religious structures, as well as the four encircling minarets. It is considered the third holiest site in Islam. The compound's main congregational mosque or prayer hall is variously known as Al-Aqsa Mosque, Qibli Mosque or al-Jāmiʿ al-Aqṣā, while in some sources it is also known as al-Masjid al-Aqṣā; the wider compound is sometimes known as Al-Aqsa Mosque compound in order to avoid confusion.

During the rule of the Rashidun caliph Umar (r. 634–644) or the Umayyad caliph Mu'awiya I (r. 661–680), a small prayer house on the compound was erected near the mosque's site. The present-day mosque, located on the south wall of the compound, was originally built by the fifth Umayyad caliph Abd al-Malik (r. 685–705) or his successor al-Walid I (r. 705–715) (or both) as a congregational mosque on the same axis as the Dome of the Rock, a commemorative Islamic monument. After being destroyed in an earthquake in 746, the mosque was rebuilt in 758 by the Abbasid caliph al-Mansur (r. 754–775). It was further expanded upon in 780 by the Abbasid caliph al-Mahdi (r. 775–785), after which it consisted of fifteen aisles and a central dome. However, it was again destroyed during the 1033 Jordan Rift Valley earthquake. The mosque was rebuilt by the Fatimid caliph al-Zahir (r. 1021–1036), who reduced it to seven aisles but adorned its interior with an elaborate central archway covered in vegetal mosaics; the current structure preserves the 11th-century outline.