Musnad Ahmed: Hadith 3457

Shall I not tell you about the prayer of the Messenger of Allah (ﷺ) when he was travelling? We said: Yes. He said: If the sun passed the meridian when he was still halting, he would put zuhr and ‘Asr together before moving on. If it had not passed the meridian whilst he was halting he would move on until it was time for ‘Asr, then he would halt and put Zuhr and ‘Asr together. If the time for Maghrib came whilst he was still halting, he would put it together with ‘Isha'. If it had not yet come whilst he still halting, he would move on until it was time for ‘Isha', then he would halt and put the two prayers together.