Sahih Muslim Book 1, Hadith Number 98.

Chapter : Din is sincerity and well-wishing.

It is narrated on the authority of Tamim ad-Dari that the Apostle of Allah (may peace and blessings be upon him) observed: Al-Din is a name of sincerity and well wishing. Upon this we said: For whom? He replied: For Allah, His Book, His Messenger and for the leaders and the general Muslims.