Musnad Ahmad 25:353

Yunus and Hassan ibn Musa—the meaning being the same—said: Hammad, meaning Ibn Zayd, narrated to us, from Ayyub, from Abu Qilabah, from Ibn Abbas, who said—and I do not know it to be anything other than him having attributed it to the Prophet (ﷺ)—he said: "When he would descend at a stopping place and the place pleased him, he would delay the Dhuhr until he joined the Dhuhr and the Asr. And when he was traveling and a stopping place was not prepared for him, he would delay the Dhuhr until he reached the stopping place, then he would join the Dhuhr and the Asr." Hassan said: "When he traveled and descended at a stopping place."