Hadith: The time for the Zhuhr prayer starts when the sun has passed its zenith and a man's shadow is equal in length to his height, until the time for the ‘Asr prayer comes. The time for the ‘Asr lasts until the sun turns yellow. The time for the Maghrib prayer lasts so long as the dusk is not gone. The time for the ‘Ishā' prayer lasts until midnight. The time for the Fajr prayer lasts from the break of dawn so long as the sun has not risen

عن عبد الله بن عمرو رضي الله عنهما : أن رسول الله صلى الله عليه وسلم ، قال:«وقت الظهر إذا زالت الشمس وكان ظل الرجل كطوله، ما لم يحضر العصر، ووقت العصر ما لم تَصْفَرَّ الشمس، ووقت صلاة المغرب ما لم يَغِبْ الشفق، ووقت صلاة العشاء إلى نصف الليل الأوسط، ووقت صلاة الصبح من طلوع الفجر ما لم تطلع الشمس، فإذا طلعت الشمس فأمسك عن الصلاة، فإنها تطلع بين قرني شيطان».
[صحيح] - [رواه مسلم]

‘Abdullāh ibn ‘Amr (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said: "The time for the Zhuhr prayer starts when the sun has passed its zenith and a man's shadow is equal in length to his height, until the time for the ‘Asr prayer comes. The time for the ‘Asr lasts until the sun turns yellow. The time for the Maghrib prayer lasts so long as the dusk is not gone. The time for the ‘Ishā' prayer lasts until midnight. The time for the Fajr prayer lasts from the break of dawn so long as the sun has not risen. When the sun rises, stop praying, for it rises between two horns of a devil."
[Authentic hadith] - [Narrated by Muslim]

Explanation

This Hadīth tells us about the prayer times: First: The time for the Zhuhr prayer starts when the sun passes the highest part of the sky and starts to descend towards the west. That is when we can see the shadow of a straight object increase and fall towards the east, and one's shadow becomes almost equal in length to his height until the time for the ‘Asr prayer comes. Second: The time for the ‘Asr starts from the point when one's shadow is equal to his height in length and lasts until the sun turns yellow. This indicates the preferred time for offering the ‘Asr. However, the Prophet (may Allah's peace and blessings be upon him) said: "Whoever prays one Rak‘ah of the ‘Asr before the sun sets has prayed it in time.'' [Al-Bukhāri and Muslim] Also: "The time for the ‘Asr lasts until the sun sets." A narration of Muslim reads: "...until the sun turns yellow and its first horn has fallen." Third: The time for the Maghrib lasts so long as the dusk has not gone. Dusk is the soft glowing light from the sky when the sun is below the horizon. So if the twilight has partially gone, then the ‘Ishā' time has not yet come. Similarly, if the sun has set partially, then the Maghrib time has not yet come. Fourth: The time for the ‘Ishā' starts when the twilight has completely faded until midnight, which is the preferred time for offering the ‘Ishā'. However, the time of necessity extends until pre-dawn. Fifth: The time for the Fajr starts from pre-dawn (true dawn) and lasts so long as the sun has not yet started to rise. When the sun starts to rise, one must not pray, because it rises between the two horns of the devil. The devil waits for the time when the sun starts to rise and stands up to be facing those who prostrate for the sun. Their prostration for the sun turns into worship of the devil. Hence, the Prophet (may Allah's peace and blessings be upon him) prohibited the Muslims to pray at that time to differentiate between those who worship Allah and those who worship the devil.