I had a fistula, so I asked the Prophet ﷺ about prayer. He said, "Pray standing. If you cannot, then sitting. If you cannot, then on your side."
حدثنا وكيع حدثنا إبراهيم بن طهمان عن حسين المعلم عن ابن بريدة
كان بي الناصور فسألت النبي ﷺ عن الصلاة فقال صل قائما فإن لم تستطع فقاعدا فإن لم تستطع فعلى جنب
Its isnad is sahih, its narrators are trustworthy and well known, and Ibn Burayda is Abdullah.The hadith was narrated by Bukhari 2/60 in the chapter on shortening the prayer, when unable to stand, by Abu Dawud 1/290, number 952, in the chapter on the prayer of one sitting, by Tirmidhi 2/207, number 371, where he said, hasan sahih, by Ibn Majah 1/386, number 1223, in the chapter on establishing the prayer, on what has been said about the prayer of the sick, and by Bayhaqi 2/304.