Narrated Abu Hurairah: The Prophet ﷺ said: When any of you prays, he should not place his sandals on his right side or on his left so as to be on the right side of someone else, unless no one is at his left, but should place them between his feet.
Hadith Referenceسنن ابي داود / كتاب الصلاة / 654
Hadith Gradingالألبانی:حسن صحيح | زبیر علی زئی:صحيح, مشكوة المصابيح (767), صححه ابن خزيمة (1016 وسنده حسن)