Although not the founder of Islamic Unity (Persis), but A Hassan is the most influential figure and a central teacher for Islamic unity. his works became the reference for the next generation to date, notably the book "Question Answer", Qur'anic commentary "Al-Furqon", and about Tawheed - which is still in part studied by santri pesantren of Islamic unity.
According to various history books, A. Hasan is a cleric figure who is active in studying Islam and active also in da'wah. He is very concerned about the young Muslims who are studying in schools owned by the Dutch colonial government which is very less to teach Islam.
Among the high school students who often come to A. Hassan's house to ask questions and discuss Islamic matters is the podium lion, who is also the Masyumi & Persatuan Islam figure, Moehammad Natsir.
Allahu Yarham A. Hassan, lahul Faatihah.
Reference: exactinin.com
Source @IndonesiaBersuhidID