Sahih Bukhari
Obligatory Charity Tax (Zakat)
Volume: 002 / Book Number: 024 / Hadith Number: 490
Narrated Ibn Masud:
I heard the Prophet saying, "There is no envy except in two: a person whom Allah has given wealth and he spends it in the right way, and a person whom Allah has given wisdom (i.e. religious knowledge) and he gives his decisions accordingly and teaches it to the others."