All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
According to authentic Sunnah, it is permissible to seek blessings in the physical traces of the Prophet, sallallaahu ‘alayhi wa sallam, like his hair, for instance, or his sweat or anything that had touched his body. This is supported by the Hadeeth narrated in the book of Imaam Muslim . This Hadeeth mentions that the Prophet, sallallaahu ‘alayhi wa sallam, distributed his hair among people in the Farewell Hajj after he shaved his head.
On the other hand, it is prohibited to seek blessings in the physical traces of anyone other than the Prophet, sallallaahu ‘alayhi wa sallam, for a number of reasons. First of all, no one should ever be compared to the Prophet, sallallaahu ‘alayhi wa sallam, because the goodness and blessings that he had been granted have not been given to anyone else.
The second reason is that this may lead to exaggeration and Shirk; (polytheism) hence, it is necessary to prohibit it as a means to eliminate unfavorable outcomes.
The third reason is that the Companions, may Allah be pleased with them, themselves did not do this with anyone else but the Prophet, sallallaahu ‘alayhi wa sallam. They did not even do this with Abu Bakr or ‘Umar who were the best people of this Nation. Had this way of seeking blessings been permissible, the Companions would have certainly sought it and would never have left it.
Hence, it is clear that seeking blessings in the physical traces of other than the Prophet, sallallaahu ‘alayhi wa sallam, is impermissible.
Allaah Knows best.