The Limits of Ablution, Its Order and Reward
Man Lā Yaḥḍuruh al-Faqīh|Volume 1|Book 1|Chapter 11
وَ رَوَتْ عَائِشَةُ عَنِ اَلنَّبِيِّ صَلَّى اَللَّهُ عَلَيْهِ وَ آلِهِ أَنَّهُ قَالَ: «أَشَدُّ اَلنَّاسِ حَسْرَةً يَوْمَ اَلْقِيَامَةِ مَنْ رَأَى وُضُوءَهُ عَلَى جِلْدِ غَيْرِهِ.
Aisha narrated from the Prophet صلى الله عليه وعلى آله وسلم, that He said: "The people with the most regret on the Day of Resurrection will be those who sees his wudu (ablution) on the skin of someone else”.
- Ṣaḥīḥ al-Faqīh