Sunan an-Nasa'i, Volume 1, Book 6, Hadith 499 (DarusSalam)

Hamzah Al-'A'idhi said: "I heard Anas bin Malik say: 'When the Prophet halted, he would not move on until he had prayed Zuhr.' A man said: 'Even if it was the middle of the day?' He said: 'Even if it was the middle of the day.'"

أَخْبَرَنَا عُبَيْدُ اللَّهِ بْنُ سَعِيدٍ، حَدَّثَنَا يَحْيَى بْنُ سَعِيدٍ، عَنْ شُعْبَةَ، قَالَ حَدَّثَنِي حَمْزَةُ الْعَائِذِيُّ، قَالَ سَمِعْتُ أَنَسَ بْنَ مَالِكٍ، يَقُولُ كَانَ النَّبِيُّ صلى الله عليه وسلم إِذَا نَزَلَ مَنْزِلاً لَمْ يَرْتَحِلْ مِنْهُ حَتَّى يُصَلِّيَ الظُّهْرَ ‏.‏ فَقَالَ رَجُلٌ وَإِنْ كَانَتْ بِنِصْفِ النَّهَارِ قَالَ وَإِنْ كَانَتْ بِنِصْفِ النَّهَارِ ‏.‏

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also referenced under: Book 6, Hadith 502 (In-Book)