Sayyiduna Abu Qatadah (may Allah be pleased with him) said that when the Messenger of Allah (peace and blessings be upon him) halted to rest at night, he would lie down on his right side; but when he halted to rest shortly before dawn, he would raise his forearm upright and rest his head on his palm.
(b) In the narration of Ibn Bishran (may Allah have mercy on him): When the Messenger of Allah (peace and blessings be upon him) halted to rest while much of the night remained, he would make his right hand his pillow; and when he halted to rest shortly before dawn, he would rest his head on the palm of his right hand and remain so for a while.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10344