One of the lights from the descendants of Prophet Muhammad (SAWS) is Imam Ali Ar-Rida (SA).
Imam Ali Ar-Rida was born in Al-Madinah during the rule of Bani Abbas. His father was Imam Musa Al-Kathim bin Ja’far As-Sadiq bin Muhammad Al-Baqir bin Ali As-Sajjad bin Al-Husayn As-Sibt bin Ali Al-Murtada bin Abi Talib (SA). Like his father, the majority of historians described him as having dark brown skin just as his father was described.
Scholars of hadith including Ahmad bin Hanbal narrated from the chain of Imam Ali Ar-Rida as well as from one of his most notable students Ma’ruf Al-Karkhi (QR). He is considered to be an imam of knowledge for madhhab Zaydi and is in the spiritual chains of At-Tariqah Al-Qadiriyyah and At-Tariqah An-Naqshabandiyyah. He is also known to be the 8th imam protected from error of madhhab Ja’fari.
Imam Ali Ar-Rida was known for his good character, austerity and knowledge. Among his scholarship which exists among us today are Sahifah Ar-Rida, a book of ahadith from the Prophet (SAWS) and sayings of Imam Ali bin Abi Talib (KW) as well as Ar-Risalah Adh-Dhahabiyyah, the 1st book compiled regarding Prophetic medicine. Among the knowledge from Imam Ali Ar-Rida which has reached us is the hadith qudsi that the Prophet (SAWS) said that Allah (SWT) said, “There is no deity except Allah is My fortress, so whoever enters My fortress, (s)he will be safe from My punishment.”
Abdullah bin Harun, the Abbasi khalifah also known by his self-appointed title “Al-Ma’mun,” publically declared that Imam Ali Ar-Rida would be his successor. Imam Ali Ar-Rida eventually went to Tus in modern day Iran where he died due to poisoning before Abdullah Al-Abbasi.
Imam Ali Ar-Rida was buried in Tus, which is currently known as Mashhad. The masjid where he is buried is currently the largest masjid in the world, even larger than Al-Masjid Al-Haram in Makkah and Al-Masjid An-Nabawi in Al-Madinah.