and Yaʿūq and Nasr.’ (Nūḥ 23).

This verse is irrefutable proof that the foremost concern of anyone who calls people to the “true Islam” must always be the summons to tawḥīd (pure monotheism). That is precisely the meaning of His words, exalted is He: “So know that there is no deity worthy of worship except Allah” (Muḥammad 19).

Such was the Prophet’s ﷺ sunnah in both practice and instruction.

Regarding his practice, there is no need for lengthy argument: during the Meccan phase, the Prophet’s actions and preaching were, for the most part, limited to calling his people to worship Allah alone with no partner whatsoever.

As for his instruction, it is illustrated by the hadith of Anas ibn Mālik—recorded in both Ṣaḥīḥ al-Bukhārī and Ṣaḥīḥ Muslim—that when the Prophet ﷺ sent Muʿādh to Yemen he said to him, “Let the first thing you invite them to be the testimony that there is no deity worthy of worship but Allah. If they obey you in that …” (1) and so forth. The remainder of the hadith is well-known, God willing.