Q: Why is kissing of the Hajre Aswad allowed in the light of Quran and Sunnah?
A: It is permissible to kiss the hajar-e-aswad because Rasulullah (Sallallaahu Alayhi wa Sallam) kissed it. The narration mentions that Sayyidina Umar (Radhiyallaahu Anhu) kissed the Hajre Aswad and thereafter addressed it with the following words: "I know that you cannot harm or give benefit. If I had not seen the Nabi (Sallallaahu Alayhi wa Sallam) kissing you, I would not have kissed you." (Bukhaari)
Kissing of the Hajre Aswad is the practice of Rasulullah (Sallallaahu Alayhi wa Sallam), and is proven from the Sunnah.