Al-Bara b. Azib said :The Messenger of Allah (May peace be upon him) said to me: when you go to bed while you are in the state of purification, lay your head on your right hand. He then mentioned the rest of the tradition in a similar manner as above.
حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، عَنْ فِطْرِ بْنِ خَلِيفَةَ، قَالَ سَمِعْتُ سَعْدَ بْنَ عُبَيْدَةَ، قَالَ سَمِعْتُ الْبَرَاءَ بْنَ عَازِبٍ، قَالَ قَالَ لِي رَسُولُ اللَّهِ صلى الله عليه وسلم " إِذَا أَوَيْتَ إِلَى فِرَاشِكَ وَأَنْتَ طَاهِرٌ فَتَوَسَّدْ يَمِينَكَ " . ثُمَّ ذَكَرَ نَحْوَهُ .
AbuDaud
General Behavior (Kitab Al-Adab) • Hadith 5047