Was Abu Bakr (may Allah be pleased with him) a Muslim monotheist before the Prophetic Mission?

Abu Bakr al-Siddiq, may Allah be pleased with him, embraced Islam after the Prophet, peace and blessings be upon him, was sent, like the rest of the Companions. It has not been authentically narrated that he believed in the Oneness of Allah and the falsehood of idol worship before Islam, as was the case with some of the Hanifs. However, the swiftness of his conversion to Islam and his intense affirmation of the Prophet, peace and blessings be upon him, as indicated by the hadith (definition) of Abu al-Darda, and his declaration that he was the first to embrace Islam, suggest that his heart was prepared for Islam and that idol worship had not taken hold of him, which indicates the soundness of his innate disposition (fitra).