When the Emigrants (al-Muhājirūn) and the Helpers (al-Anṣār) had gathered together—and everyone who accepted Islam came to join them—Allah then set down the remainder of the religious laws. He made fasting and zakah obligatory upon His Prophet ﷺ in the second year after the Hijrah, and, according to the soundest view, He made Hajj obligatory in the ninth year after the Hijrah. In this way the pillars of Islam were perfected: the first is the two testimonies of faith, and the last is the pilgrimage to Allah’s Sacred House.

The conclusion to be drawn is that tawḥīd (pure monotheism) is the primary duty in calling people to Allah. The caller must begin with it before addressing prayer, fasting, zakah, or Hajj, for the Prophet ﷺ spent ten years inviting people to tawḥīd and forbidding polytheism, while no command was yet given for prayer, zakah, Hajj, or fasting. Those obligations were only imposed once tawḥīd had been firmly established.

Thus, whenever the Prophet ﷺ sent out preachers, he ordered them to summon the people first to tawḥīd, as in the ḥadīth of Muʿādh: “You are going to a people of the Scripture, so let the first thing to which you call them be the testimony that there is no deity worthy of worship except Allah and that Muhammad is the Messenger of Allah. If they respond to that, then inform them that Allah has made five daily prayers obligatory upon them…”—and so on.