Shama-il Tirmidhi Chapter 032, Hadith Number 005 (211).

Abu Uthman An-Nahdi (At-Taabi’ee) radiyallahu anhu relates that Rasoolullah sallallahu alaihe wasallam said: If one is given rayhaan, he should not refuse it, because it originates from Jannah.

Commentary
From this, is it only the rayhaan itself that is meant or other fragrant substances also included? The linguists give both meanings, and both may be intended here. Allah Ta’aala made an imitation of the fragrance of Jannah in this world, because this may be an incentive for the people towards Jannah, and also increase their desire and zeal for it. People are naturally attracted to something fragrant. What comparison can there be made with the original fragrance of Jannah. It shall have such a strong fragrance, that the distance of five hundred years will have to be covered to reach its source.