A man came to the Prophet ﷺ and said, "I performed the major ritual bath after sexual impurity and prayed the dawn prayer. Then, when morning came, I noticed a spot the size of a fingernail that the water had not reached."The Messenger of Allah ﷺ replied, "If you had simply wiped it with your hand, that would have been enough."
حدثنا سويد بن سعيد حدثنا أبو الأحوص عن محمد بن عبد الله عن الحسن بن سعد عن أبيه
جاء رجل إلى النبي ﷺ فقال إني اغتسلت من الجنابة وصليت الفجر ثم أصبحت فرأيت قدر موضع الظفر لم يصبه الماء فقال رسول الله ﷺ لو كنت مسحت عليه بيدك أجزأك
No references are available.
[Its chain of transmission is very daif] Busiri said, This chain is daif because of the weakness of Muhammad bin Ubaydullah Arzami, since he is discarded (as narrator) (Taqrib).