النوم على الشق الأيمن
A recommended sleeping posture — lying on the right side after performing ablution — paired with a protective supplication before sleep.
إِذَا أَتَيْتَ مَضْجَعَكَ فَتَوَضَّأْ وُضُوءَكَ لِلصَّلَاةِ، ثُمَّ اضْطَجِعْ عَلَى شِقِّكَ الْأَيْمَنِ
“When you go to your bed, perform ablution as you would for prayer, then lie down on your right side.” (meaning, not a literal translation)
Ibn al-Qayyim notes physicians of his era already associated right-side sleeping with easier digestion, since it was thought to position the stomach favorably relative to the liver.