Has Allah (SWT) conferred authority on Prophet Muhammad (PBUH) to forgive sins of all and sundry or is forgiving sins the exclusive prerogative of Allah?
Forgiveness of sins is in the hands of Allah (SWT) who gave the Prophet (SAWA) the greatest status of intercession ( Shafa'ah) and made it very clear in Quran that those who commit sinful acts should come to the Prophet so that he seeks forgiveness for them ( Had those who did wrong to themselves, come to you and begged for Allah's forgiveness, and the messenger had prayed for their forgiveness, they would have found Allah accepting their repentance and Merciful) Sura 4, Verse 64.
Wassalam.