354 – Anas (may Allah be pleased with him) reported: “Whenever the Messenger of Allah ﷺ set out on a journey before the sun had begun to decline, he would delay the Zuhr prayer until the time of ʿAsr; then he would dismount and perform the two together. But if the sun had already started to decline before he departed, he would pray Zuhr first and then mount.” Agreed upon.

In al-Ḥākim’s narration in al-Arbaʿīn, with an authentic chain: “He prayed Zuhr and ʿAsr and then mounted.”

Abū Nuʿaym relates in his Mustakhraj ʿalā Muslim: “Whenever he was on a journey and the sun had passed its zenith, he would pray Zuhr and ʿAsr together and then resume the journey.” ⦗1⦘

— Hadith grading:
The basic report is found in the two Ṣaḥīḥs. As for al-Ḥākim’s additional wording, Ibn Ḥajar said in Fatḥ al-Bārī (2/583): “It is an authentic, though singular, addition.” Al-Mundhirī and al-ʿIlāʾī also judged it sound through this chain. As for Abū Nuʿaym’s version, al-Nawawī declared it authentic, as noted in at-Talkhīṣ (2/49).

— Key vocabulary:
• tazīgh al-shams: the moment the sun begins to lean westward after reaching the meridian.
• zālat al-shams: the sun’s inclination westward after standing at the very zenith.