Muwatta Malik #191
Prayer
Yahya related to me from Malik from Nafi that Abdullah ibn Umar,
when asked if anyone should recite behind an imam, said, "When you
pray behind an imam then the recitation of the imam is enough for you
and when you pray on your own you must recite." Nafi added, "Abdullah
ibn 'Umar used not to recite behind the imam."
Yahya said
that he heard Malik say, "The position with us is that aman recites
behind the imam when the imam does not recite aloud and he refrains
from reciting when the imam recites aloud."
About Muwatta Malik
This hadith is #191 from Muwatta Malik, in the Book of Prayer. Muwatta Malik contains 1,985 hadiths across 61 books.