عَنْ أَبِي هُرَيْرَةَ رَضِيَ اللَّهُ عَنْهُ عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَآلِهِ وَسَلَّمَ قَالَ: ((مَنْ أَفْضَى بِيَدِهِ إِلَى ذَكَرِهِ لَيْسَ دُونَهُ سِتْرٌ فَقَدْ وَجَبَ عَلَيْهِ الْوُضُوءُ))
It is narrated from Sayyiduna Abu Hurairah (may Allah be pleased with him) that the Noble Prophet (peace and blessings be upon him and his family) said: Whoever touches his private part with his hand, while there is no covering in front of him, then indeed, ablution becomes obligatory upon him.