What is the proof for the permissibility of seeking the blessings (tabarruk) by certain creations?

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Seeking the blessings from the Prophet, sallallahu ^alayhi wa sallam, and his traces is permissible.  In narration about Yusuf, Ayah 93 in Surat Yusuf, means, “Take my shirt and cast it over the face of my father; His sight will return to him.” al-Bukhariyy and Muslim narrated a hadith in which the Prophet divided his hair and distributed it amongst the people. Obviously, he did not give his hair to be eaten, but for people to seek blessings by them.