Musnad Ahmad 2:293

Abu Ahmad narrated to us, Sufyan narrated to us, from Alqamah ibn Marthad, from Sulayman ibn Buraydah, from Ibn Ya'mar, who said: I asked Ibn Umar, or a man asked him: "We travel in this land and we meet people who say: 'There is no decree (Qadar).'" Ibn Umar said: "If you meet those people, inform them that Abdullah ibn Umar is innocent of them, and they are innocent of him"—he said it three times. Then he began to narrate to us, saying: "While we were with the Messenger of Allah, may Allah bless him and grant him peace, a man came and said: 'O Messenger of Allah, may I draw near?' He said: 'Draw near.' So he drew near by a step. Then he said: 'O Messenger of Allah, may I draw near?' He said: 'Draw near.' So he drew near by a step. Then he said: 'O Messenger of Allah, may I draw near?' He said: 'Draw near.' So he drew near by a step, until his knees almost touched the knees of the Messenger of Allah, may Allah bless him and grant him peace. He said: 'O Messenger of Allah, what is faith?'" Then he mentioned its meaning.