The author, may Allāh have mercy on him, began with this foundation, which is the most fundamental foundation, namely the tawḥīd of Allāh, Glorified and Exalted. He said, may Allāh have mercy on him: [The first foundation: Sincerity of religion for Allāh alone, with no partner, and an explanation of its opposite, which is shirk with Allāh, and how most of the Qurʾān explains this foundation in various ways with language that even the simplest of people can understand. Yet, when most of the ummah fell into what they did, Satan presented sincerity as diminishing the righteous and neglecting their rights, and presented shirk with Allāh as love for the righteous and following them]. This is the first of the six important foundations. The foundation in this world and in this existence is the worship of Allāh, Glorified and Exalted, about which Allāh, Glorified and Exalted, said: "And I did not create the jinn and mankind except to worship Me" (Sūrah al-Dhāriyāt, 56), and which was commanded in the beginning of the Wise Book; for the first command in the Book of Allāh is the command of tawḥīd in His saying: "O mankind, worship your Lord, who created you and those before you, that you may become righteous" (Sūrah al-Baqarah, 21). The first address in the Wise Book directed to people in general is the command of tawḥīd, which indicates the importance and seriousness of this matter and the obligation to pay attention to it. He, may Allāh have mercy on him, said: [Sincerity of religion for Allāh alone, with no partner]. (Sincerity) means: purification. It is a noun meaning: purifying the religion. Religion is the action intended to be made sincere for Allāh, meaning: purifying the action. The meaning of purifying and making it sincere: freeing it from every impurity and association with Allāh, Glorified and Exalted. Sincerity of action means freeing it from any share for other than Allāh, Glorified and Exalted. The action includes the action of the heart and the action of the limbs—the apparent action—thus encompassing both internal and external actions, and includes obligatory and recommended actions, for all must be made sincere for Allāh, Glorified and Exalted. Is there evidence in the Book indicating that religion comes in the meaning of action? The answer: Yes. It is the saying of Allāh, Exalted: "Unquestionably, for Allāh is the pure religion" (Sūrah al-Zumar, 3), and His saying: "For you is your religion, and for me is my religion" (Sūrah al-Kāfirūn, 6), meaning: for you is your action and for me is my action. As for His saying "Master of the Day of Judgment" (Sūrah al-Fātiḥah, 4), religion here means recompense and accountability, not action. Thus, it does not mean: Master of the Day of Action; because the day of action is this world, whereas the Hereafter is not a place of action, but rather a place of accountability and recompense. He, may Allāh have mercy on him, said: [Sincerity of religion for Allāh alone, with no partner]. Would it not have sufficed to say: [Sincerity of religion for Allāh] without saying: [alone, with no partner]? The answer: Yes. But his saying: [alone, with no partner] is an emphasis on the meaning of sincerity, for (alone) emphasizes the meaning of tawḥīd, and (with no partner) emphasizes the negation of shirk, that He has no partner, Glorified and Exalted, in any of His matters, no partner in His dominion, no partner in His creation, no partner in His lordship, no partner in His divinity, no partner in His names and attributes, and no partner in what is due to Him of worship. Thus, Allāh must be singled out for all that He deserves, for Allāh, Glorified and Exalted, is unlike anything in any of His affairs, as He said about Himself: "There is nothing like unto Him, and He is the Hearing, the Seeing" (Sūrah al-Shūrā, 11).