upon all Muslims, nor did he say, “it is obligatory upon some of them.” Rather, he declared, “it is obligatory upon us,” that is, upon every single one of us as an individual duty.

Before we enter into the detailed questions, let us also understand that the knowledge the ummah must acquire—whether as a personal obligation or as a collective one—is the sacred knowledge brought by the Messenger ﷺ.

By contrast, worldly sciences such as the knowledge of industries and crafts, arithmetic, mathematics, and engineering are permissible to study, and they may become obligatory when the community needs them, in which case the duty falls upon those who are able. Yet this is not the knowledge intended in the Quran and Sunnah, the knowledge whose possessors Allah has praised and commended, and concerning which the Prophet ﷺ said, “The scholars are the heirs of the prophets.” That intended knowledge is the sacred knowledge.

As for worldly sciences, there is no sin upon the one who is ignorant of them, and whoever learns them does so lawfully; if he benefits the ummah through them, he will be rewarded and compensated. Should a person die without ever learning such sciences, he will not be called to account for that on the Day of Resurrection. But whoever dies while ignorant of the sacred knowledge—especially