The Messenger of Allah ﷺ said, "When one of you prays, he should not place his sandals on his right side, nor on his left, for they will then be on the right side of someone else, unless there is no one on his left. Rather, let him place them between his feet."
حدثنا الحسن بن علي حدثنا عثمان بن عمر حدثنا صالح بن رستم أبو عامر عن عبد الرحمن بن قيس عن يوسف بن ماهك
أن رسول الله ﷺ قال إذا صلى أحدكم فلا يضع نعليه عن يمينه ولا عن يساره فتكون عن يمين غيره إلا أن لا يكون عن يساره أحد وليضعهما بين رجليه
No references are available.
[Sahih]Bayhaqi related it, 2/432, from the hadith of Abu Dawud with the same wording. Ibn Khuzayma graded it sahih, no. 1016, as did Ibn Hibban, no. 361, and Hakim according to the criteria of the two Shaykhs, 1/259, and Dhahabi agreed with him. Its chain of transmission is hasan, and the hadith has corroborating narrations, see the following hadith.