Hadith: I saw you pray towards a direction other than the Qiblah! He said: Had I not seen the Messenger of Allah (may Allah's peace and blessings be upon him) doing so, I would not have done it

عن أنس بن سيرين قال: «اسْتَقبَلنَا أَنَسًا حِين قَدِم مِن الشَّام، فَلَقِينَاه بِعَينِ التَّمرِ، فَرَأَيتُهُ يُصَلِّي على حِمَار، وَوَجهُهُ مِن ذَا الجَانِب -يعني عن يَسَارِ القِبلَة- فقلت: رَأَيتُك تُصَلِّي لِغَيرِ القِبلَة؟ فقال: لَولاَ أنِّي رَأيتُ رسول الله صلى الله عليه وسلم يَفْعَلُه ما فَعَلتُه».
[صحيح] - [متفق عليه]

Anas ibn Sirīn reported: 'We received Anas [ibn Mālik] when he returned from Syria and met him at ‘Ayn At-Tamr. I saw him pray on a donkey, and his face was to this side, i.e. to the left side of the Qiblah. I said to him: "I saw you pray towards a direction other than the Qiblah!" He said: "Had I not seen the Messenger of Allah (may Allah's peace and blessings be upon him) doing so, I would not have done it."
[Authentic hadith] - [Narrated by Bukhari & Muslim]

Explanation

Anas ibn Mālik (may Allah be pleased with him) returned from Syria and people received him because of his high status and wide knowledge. The narrator, who was among the people who received him, saw him pray on on a donkey towards the left side of the Qiblah. He asked him about that, and Anas told them that he had seen the Prophet (may Allah's peace and blessings be upon him) do that; otherwise, he would not have done it.