Mishkat al-Masabih
Abu Qatada told that when God's Messenger encamped at night on a journey he lay down on his right side, and when he encamped a little before morning he raised his forearm and placed his head on the palm of his hand. Muslim transmitted it.
عَن أبي قتادةَ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ إِذَا كَانَ فِي سَفَرٍ فَعَرَّسَ بِلَيْلٍ اضْطَجَعَ عَلَى يَمِينِهِ وَإِذَا عَرَّسَ قُبَيْلَ الصُّبْحِ نَصَبَ ذِرَاعَهُ وَوَضَعَ رَأْسَهُ عَلَى كَفِّهِ. رَوَاهُ مُسلم
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