Abu Dawud Book 2, Hadith Number 1325.

Chapter : Recitation of the quran in loud voice during the prayer at night.

Narated By N/A : This tradition has also been transmitted by Abu Hurairah through a different chain of narrators. This version does not mention the Prophet (PBUH) said to Abu Bakr: Raise your voice a little; or he said to ‘Umar : Lower your voice a little. But this version adds: (the Prophet said:) I heard you, Bilal,(reciting); you were reciting partly from this surah and partly from that surah. He said: This is all good speech; Allah has combined one part with other. The Prophet (PBUH) said: All of you were correct.