Muwatta Malik 326

حَدَّثَنِي يَحْيَى، عَنْ مَالِكٍ، عَنْ دَاوُدَ بْنِ الْحُصَيْنِ، عَنِ الأَعْرَجِ، عَنْ أَبِي هُرَيْرَةَ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم كَانَ يَجْمَعُ بَيْنَ الظُّهْرِ وَالْعَصْرِ فِي سَفَرِهِ إِلَى تَبُوكَ ‏.‏

Yahya related to me from Malik from Da'ud ibn al-Husayn from al- Araj from Abu Hurayra that the Messenger of Allah, may Allah bless him and grant him peace, joined dhuhr and asr on his journey to Tabuk

Reference

Muwatta Malik 326

In-book

Book 9, Hadith 1