It is narrated from Abu Nadrah: We were engaged in a discussion of knowledge with Sayyiduna Imran bin Husayn (may Allah be pleased with him). A man said: "Do not speak of anything except the Qur'an." Sayyiduna Imran bin Husayn (may Allah be pleased with him) said to him: "You are truly a fool and a simpleton! Did you find in the Qur'an that you should pray four rak'ahs of Zuhr, and four of Asr as well, without reciting aloud in them; and pray three rak'ahs of Maghrib, reciting aloud in two and quietly in one; and pray four rak'ahs of Isha, reciting aloud in two and quietly in two; and pray two rak'ahs of Fajr, reciting aloud in both?"
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 3069