I say, and with God's success: It starts from the last time of Dhuhr until sunset, and what is considered in sunset is the falling of the sun's disk, which is evident in the desert. As for in buildings and the peaks of mountains — meaning their highest points — it is when no ray of it is seen on the edges of the buildings and mountain peaks, and when darkness begins to approach from the east; for Abu Huraira, may God be pleased with him, said that the Prophet, peace be upon him, said: "Indeed, for prayer there is a beginning and an end. The first time for Dhuhr prayer is when the sun has passed its zenith, and its last time is when the time for Asr enters. The first time for Asr prayer is when its time enters, and its last time is when the sun turns yellow. The first time for Maghrib is when the sun sets, and its last time is when the twilight disappears. The first time for Isha is when the twilight disappears, and its last time is when midnight is reached. The first time for Fajr is when dawn breaks, and its last time is when the sun rises." In Sunan al-Tirmidhi 1: 284, and its narrators are the narrators of the group except for Hanad, as mentioned in I'la al-Sunan 2: 10. And from Abdullah ibn Rafi', the freedman of Umm Salamah, the wife of the Prophet, peace be upon him, that he asked Abu Huraira, may God be pleased with him, about the time of prayer, and Abu Huraira said: "I will inform you: Pray Dhuhr when your shadow is equal to you, and Asr when your shadow is twice your length, and Maghrib when the sun sets, and Isha is between you and a third of the night, and pray Fajr in the twilight, meaning the early dawn." In Al-Muwatta of Malik 1: 8, and Musannaf Abdul Razzaq 1: 450, and its chain of narration is authentic as in I'la al-Sunan 2: 9. From Jabir, may God be pleased with him, he said: "Gabriel, peace be upon him, came to the Prophet, peace be upon him, when the sun had passed its zenith and said: 'Get up, O Muhammad, and pray Dhuhr when the sun has tilted.' Then he stayed until the shadow of a man was equal to him and came to him for Asr, saying: 'Get up, O Muhammad, and pray Asr.' Then he stayed until the sun set and came to him, saying: 'Get up and pray Maghrib.' So he stood and prayed it when the sun had set. Then he stayed until the twilight disappeared and came to him, saying: 'Get up and pray Isha.' So he stood and prayed it. Then he came to him when dawn was very bright in the morning, saying: 'Get up, O Muhammad, and pray.' So he stood and prayed Fajr. Then he came to him the next day when the shadow of a man was equal to him, saying: 'Get up, O Muhammad, and pray.' So he prayed Dhuhr. Then Gabriel, peace be upon him, came to him when the shadow of a man was twice his length, saying: 'Get up, O Muhammad, and pray.' So he prayed Asr. Then he came to him for Maghrib when the sun set at one time that did not change, saying: 'Get up and pray.' So he prayed Maghrib. Then he came to him for Isha when a third of the first night had passed, saying: 'Get up and pray.' So he prayed Isha. Then he came to him for Fajr when it was very bright, saying: 'Get up and pray.' So he prayed Fajr, saying: 'What is between these two times is all a time for prayer.'" In Sunan al-Nasa'i al-Kubra 1: 471, and Al-Mujtaba 1: 263. See: Umdat al-Ri'aya 1: 147, and God knows best.