Mishkat al-Masabih
Mishkat al-Masabih 469
وَعَنْ شُعْبَةَ قَالَ: إِنَّ ابْنَ عَبَّاسٍ رَضِيَ اللَّهُ عَنْهُ كَانَ إِذَا اغْتَسَلَ مِنَ الْجَنَابَةِ يفرغ بِيَدِهِ الْيُمْنَى عَلَى يَدِهِ الْيُسْرَى سَبْعَ مِرَارٍ ثُمَّ يَغْسِلُ فَرْجَهُ فَنَسِيَ مَرَّةً كَمْ أَفْرَغَ فَسَأَلَنِي كم أفرغت فَقُلْتُ لَا أَدْرِي فَقَالَ لَا أُمَّ لَكَ وَمَا يَمْنَعُكَ أَنْ تَدْرِيَ ثُمَّ يَتَوَضَّأُ وُضُوءَهُ لِلصَّلَاةِ ثُمَّ يُفِيضُ عَلَى جِلْدِهِ الْمَاءُ ثُمَّ يَقُولُ هَكَذَا كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يتَطَهَّر. رَوَاهُ أَبُو دَاوُد
Shuʿba said that when Ibn ʿAbbās performed the ritual bath after sexual impurity, he poured water from his right hand onto his left seven times, then washed his private parts. Once he forgot how many times he had poured it and asked me. I said: ‘I don’t know.’ He said: ‘You should have known! What kept you from knowing?’ He would then perform ablution as for prayer, pour water over his body, and say: ‘This is how the Messenger of Allah purified himself.’ Abū Dāwūd transmitted it.