Sahih Muslim
The Book of Faith (Kitab Al-Iman)
Book Number: 001 / Hadith Number: 62
It is narrated on the authority of Sufyan b. 'Abdulla al-Thaqafi that he said: I asked the Messenger of Allah to tell me about Islam a thing which might dispense with the necessity of my asking anybody after you. In the hadith of Abu Usama the (words) are: other than you. He (the Holy Prophet) remarked: Say I affirm my faith in Allah and then remain steadfast to it.