Sunan Ibn Majah, Chapter: The Book of the Sunnah

"When Adi bin Hatim came to Kufah, we came to him with a delegation of the Fuqaha of Kufah and said to him: 'Tell us of something that you heard from the Messenger of Allah (saw).' He said: 'I came to the Prophet (saw) and he said: "O 'Adi bin Hatim, enter Islam and you will be safe." I said, "Whats is Islam?" He said: "To testify to La ilaha illallah (none has the right to be worshipped but Allah) and that I am the Messenger of Allah, and to believe in all the Divine Decrees, the good of them and the bad of them, the sweet of them and the bitter of them." (Daif)