Sahih al-Bukhari 1110
Sahih al-Bukhari · Book 18: Shortening the Prayers (At-Taqseer) · Should the Adhan and Iqama be pronounced when the Maghrib and Isha prayers are offered together
Narrated Anas bin Malik:
حَدَّثَنَا إِسْحَاقُ ، حَدَّثَنَا عَبْدُ الصَّمَدِ ، حَدَّثَنَا حَرْبٌ ، حَدَّثَنَا يَحْيَى ، قَالَ حَدَّثَنِي حَفْصُ بْنُ عُبَيْدِ اللَّهِ بْنِ أَنَسٍ ، أَنَّ أَنَسًا ـ رضى الله عنه ـ حَدَّثَهُ أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَجْمَعُ بَيْنَ هَاتَيْنِ الصَّلاَتَيْنِ فِي السَّفَرِ. يَعْنِي الْمَغْرِبَ وَالْعِشَاءَ.
Whenever the Prophet (ﷺ) started a journey before noon, he used to delay the Zuhr prayer till the time of `Asr and then offer them together; and if the sun declined (at noon) he used to offer the Zuhr prayer and then ride (for the journey).