Abdul Baha would attend Muhammad 'Abduh's study sessions

He [Rashid Ridá] says that when 'Abduh [one of the key figures of Islamic Modernism and the Salafi movement, also an opponent of the Ottoman ulama] was living in Beirut (presumably in the late 1880s) 'Abdu'l-Bahá more than once came to Beirut from Haifa and would make a point of attending some of Muḥammad 'Abduh's study sessions. Bahá'í sources, however, speak of only one encounter between 'Abdu'l-Bahá and 'Abduh, and the matter of how intimate the two men were bears more investigation. After 'Abduh returned to Cairo, he continued to correspond with 'Abdu'l-Bahá, and Ridá said that he had in his possession some of the latter's letters to 'Abduh.

Juan R.I. Cole. "Muhammad `Abduh and Rashid Rida: A Dialogue on the Baha'i Faith." World Order Vol. 15, nos. 3-4 (Spring/Summer 1981):7-16.

https://www.h-net.org/~bahai/diglib/articles/A-E/cole/abduh/abduh.htm