I think he attributed it to the Prophet (ﷺ) - said: If he halted in a place and liked the place he had halted, he would delay Zuhr so that he could put Zuhr and ‘Asr together, If he was travelling and did not find a place to halt, he would delay Zuhr until he came to a halting place, then he would put Zuhr and ’Asr together.