What was the religion of Abu Taalib before our Prophet, sallallaahu alayhi wa sallam, declared Islam as the right path?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Abu Taalib was upon the religion of his people, his father and grandfathers before Muhammad was made a Prophet, and he stayed on this belief until he died as an idolater. However, he supported and defended the Prophet and showed his sympathy to Islam in his poetry and prose and in all his stands. Nonetheless, he stayed on the religion of his people until he died, as mentioned in the books of Sunnah (Prophetic tradition) and biography.

Allaah Knows best.