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 (DE)
English reference (DE): Book 32, Hadith 211 (DE)
Arabic reference (DE): Book 33, Hadith 221 (DE)