Sahih Muslim
The Book of Faith (Kitab Al-Iman)
Book Number: 001 / Hadith Number: 64
'Abdullah b. Amr b. al-As is reported to have said: Verily a person asked the Messenger of Allah (may peace and blessings be upon him) who amongst the Muslims was better. Upon this (the Holy Prophet) remarked: From whose hand and tongue the Muslims are safe.