Allah, exalted be His praise, says: "Establish the prayer from the declining of the sun." [Surah al-Isra: 78]
Imam al-Shafi'i (may Allah be pleased with him) said: "The duluk of the sun means its zawal (declining)."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / Q1704
It is narrated from Sayyiduna Ibn Umar (may Allah be pleased with them both) that "the declining of the sun" (duluk al-shams) [Surah al-Isra: 78] means its inclining after midday.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1704
It is narrated from Sayyiduna Ibn Abbas (may Allah be pleased with them both) that "the declining of the sun" (duluk al-shams) [Surah al-Isra: 78] means its zawal (passing the meridian).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1705
It is narrated from Sayyiduna Abdullah bin Amr (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) was asked about the time of prayer, and he (peace and blessings be upon him) said: "The time of the Fajr prayer lasts as long as the first edge of the sun has not risen; the time of the Zuhr prayer is when the sun has declined from the middle of the sky, as long as the time of Asr has not come; the time of the Asr prayer is as long as the sun has not turned yellow and its first edge has not set; the time of the Maghrib prayer is when the sun has set, as long as the redness of twilight has not ended; and the time of the Isha prayer is until half the night."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1706
It is narrated from Sayyiduna Abdullah bin Amr bin al-As (may Allah be pleased with them both) that the Messenger of Allah (peace and blessings be upon him) said: "The time of the Zuhr prayer is when the sun has declined and a man's shadow has become equal to his height, as long as the time of Asr has not come."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1707
Al-Aswad narrates that Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) said: In summer the measure of the prayer of the Prophet (peace and blessings be upon him) was from three feet to five feet, and in winter from five to seven feet.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 1708