[Machine] He used to say, "Whoever touches his private parts, then it is obligatory for him to perform ablution." We were informed about that from Aisha and Abu Hurairah, and Al-Shafi'i reported it in his book Al-Qadim from Muslim and Sa'eed from Ibn Juraij from Ibn Abi Mulaykah that Umar ibn Al-Khattab, while leading the people in prayer, made a mistake and touched his private parts. He then signaled to the people to stay and left. He performed ablution and then returned to complete the remaining prayer with them.  

أَنَّهُ كَانَ يَقُولُ مَنْ مَسَّ ذَكَرَهُ فَقَدْ وَجَبَ عَلَيْهِ الْوُضُوءُ وَرُوِّينَا فِي ذَلِكَ عَنْ عَائِشَةَ وَأَبِي هُرَيْرَةَ وَرَوَى الشَّافِعِيُّ فِي كِتَابِ الْقَدِيمِ عَنْ مُسْلِمٍ وَسَعِيدٍ عَنِ ابْنِ جُرَيْجٍ عَنِ ابْنِ أَبِي مُلَيْكَةَ أَنَّ عُمَرَ بْنَ الْخَطَّابِ بَيْنَا هُوَ يَؤُمُّ النَّاسَ إِذْ زَلَّتْ يَدُهُ عَلَى ذَكَرِهِ فَأَشَارَ إِلَى النَّاسِ أَنِ امْكُثُوا ثُمَّ خَرَجَ فَتَوَضَّأَ ثُمَّ رَجَعَ فَأَتَمَّ بِهِمْ مَا بَقِيَ مِنَ الصَّلَاةِ