What is the interpretation of the noble verses (Say, "Shall We inform you of the greatest losers in [their] deeds? [They are] those whose effort is lost in worldly life, while they think that they are doing good work." Those are the ones who disbelieve in the verses of their Lord and His meeting, so their deeds have become worthless, and We will not establish for them on the Day of Resurrection any weight.) [Al-Kahf/103-105]? And does the description of "the greatest losers in [their] deeds" apply to Muslims? And does it include those who do not follow the Prophet in letting their beards grow? And did the Prophet pray for forgiveness for those who shave their beards?

The aforementioned verse from Surat al-Kahf was revealed concerning the disbelievers of Quraysh. It describes disbelievers who were led astray by devils, who beautified their deeds for them, and they thought they were guided. Its meaning includes Jews, Christians, and people of innovation and misguidance, according to their misguidance and their transgression of the Sharia. Deeds are entirely nullified for disbelievers, polytheists, and apostates. As for the deeds of Muslims who are people of innovation, only those deeds that are innovative and violate the Sharia are nullified.

The Hadith "O Allah, have mercy on those who shave [their heads]" has no relation to shaving the beard; rather, it pertains specifically to shaving or shortening the hair of the head upon exiting the state of ihram during Hajj and Umrah.