Sahih Muslim
The Book of Faith (Kitab Al-Iman)
Book Number: 001 / Hadith Number: 98
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.