It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that the Prophet (peace and blessings be upon him) said: "The time of Zuhr is when the sun has declined and a man's shadow has become equal to his length, as long as the time of Asr has not come; the time of Asr is as long as the sun has not turned yellow; and the time of Maghrib is as long as the redness of twilight has not disappeared." Shu'bah said: As long as the glow (thawr) of the twilight has not faded. "And the time of Isha is between you and the middle of the night, and the time of Subh is from when dawn breaks, as long as the sun has not risen."
Shu'bah said: Sometimes he narrated it as marfu' (from the Prophet) and sometimes he did not.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1712