Why was the shaving of the beard considered obligatory based on the Hadith: "Be different from the polytheists; let your beards grow, and trim your mustaches," while dyeing hair was considered merely recommended based on the Hadith: "Jews and Christians do not dye their hair, so be different from them," despite the similarity in the two Hadiths' commands?

There are fundamental differences between the ruling on growing a beard and dyeing gray hair. The command to grow a beard has not been definitively interpreted as obligatory, whereas it is authentically reported that the Prophet (peace be upon him) generally did not dye his hair, and there is nothing to indicate that dyeing hair is obligatory. Scholars have agreed that it is not obligatory.

Furthermore, many jurists have unanimously agreed on the obligation of growing a beard, while Imam Al-Tabari narrated the consensus of the predecessors and successors on the non-obligation of dyeing gray hair. It has not been authentically reported that any of the noble Companions shaved his beard, whereas it has been authentically reported that many of them left their gray hair white.

In addition, the hadiths that encourage growing a beard are more emphatic and numerous. The Prophet (peace be upon him) called it one of the practices of fitra (natural disposition) and stated that Allah commanded him with it, whereas the hadiths regarding dyeing gray hair vary.

In summary, growing a beard is obligatory according to the majority of scholars, while dyeing gray hair is recommended but not obligatory. Each ruling has its own reason and justification.