I heard Wabisa bin Mabad say, "I saw the Messenger of Allah ﷺ praying, and when he bowed, he would level his back so evenly that if water were poured on it, it would settle there."
حدثنا إبراهيم بن محمد بن يوسف الفريابي حدثنا عبد الله بن عثمان بن عطاء حدثنا طلحة بن زيد
سمعت وابصة بن معبد يقول رأيت رسول الله ﷺ يصلي فكان إذا ركع سوى ظهره حتى لو صب عليه الماء لاستقر
No references are available.
[Daif] Busiri graded it daif, and its chain of transmission is very weak. The hadith has supporting reports, but they are also weak.