THE FIRST OBLIGATION is declaring the two testimonies of faith and worshipping Allāh upon Tawḥīd. This opposes the claim of the people of speculative theology (Ahl al-Kalām) that the first obligation is rationally proving Allāḥ’s existence, or starting from a position of doubt about Allāh’s existence and subsequently removing the doubt through rational investigation to establish His existence. This is futile because affirmation of a creator is innate and rooted in original disposition (fiṭrah) and is necessary (ḍarūriyy), meaning, not in need of observation and deduction or in need of the physical senses for it to be attained.
There is innate knowledge and acquired knowledge. The former does not require any observation and analysis and is known intuitively, immediately. The second is acquired through the physical senses, through observation and analysis. Examples of the first are that a thing cannot be in two places at the same time, or exist and not exist at the same time, or the knowledge that the whole is greater than the part. These are rudimentaries, rooted in innated disposition and intuition, and provide the foundational basis for the intellect and its activity. Examples of the second are locating the direction of the qiblah, or determining the cause of an effect (in the study of creation), or the knowledge of whether the earth is stationary or in motion, or discovering that three is one-eighth of 24 and so on.
The knowledge that the world has a Maker and Creator is innate, intuitive knowledge, it is rooted in the fiṭrah, and every child is born upon this.
As such the first obligation in Islām is not to prove the existence of a Creator, but to declare the two testimonies (shahādatān), which are that none is to be worshipped but Allāh and He is not worshipped except through what He legislated through His Messenger (صلى الله عليه وسلم).
Ibn Taymiyyah (رحمه الله):
The Prophet (صلى الله عليه وسلم) did not invite anyone from the creation to observation (as a starting point for īmān), and nor to mere affirmation of a Creator Rather, the first of what he called them to was the shahādatān, he commanded his Companions with that. And this is from what the leading imāms in religion and scholars of the Muslims are united upon.
Ibn Taymiyyah (رحمه الله) said:
The Salaf and the leading scholars are agreed that the first of that which the servants are commanded with are the Shahādatān, and that whoever does that before maturity is not commanded to renew them following maturity.
Ibn al-Qayyim (رحمه الله) said:
Tawḥīd is the first of that by which Islām is entered into and the last of that by which the world is departed from.
Ibn Kathīr (رحمه الله) said:
The first obligation upon the servants is to know that there is none worthy of worship but Allāh alone, without any partners.
Shaykh Muḥammad bin Abd al-Wahhāb (رحمه الله) said:
“Know that Allāh obligated knowledge of the testimony of (لا إله إلا الله) before the obligation of prayer and fasting. That a servant investigates the meaning of [the kalimah] is greater (in obligation) than the obligation of his investigation of [the rulings of] prayer and fasting, and the unlawfulness of shirk and believing in the ṭāghūt is greater than the unlawfulness of marrying mothers and aunties.
Shaykh al-Fawzān (رحمه الله) said:
The first obligation upon the servants is the worship of Allāh. As for knowing Him, then they know Him through the fiṭrah, the intellects, creational evidences and Qurʾānic evidences.