Abu Qatadah (May Allah be pleased with him) reported:
When the Messenger of Allah ﷺ encamped at night during a journey, he would lie down on his right side, and when he stayed a little before dawn he would raise his forearm and place his head on the palm of his hand.

[Muslim].

وعن أبي قتادة، رضي الله عنه، قال: كان رسول الله ﷺ ، إذا كان في سفر، فعرس بليل اضطجع علي يمينه وإذا عرس قبيل الصبح نصب ذراعه، ووضع رأسه علي كفه" ((رواه مسلم)).