"He would sprinkle his private parts with it." [1] Shaikh Ibn As-Sunni said: "Al-Hakam (one of the narrators) is Ibn Sufyan Ath-Thaqafi. [1] The purpose is to ward off devilish whispers lest the person think any emission has taken place, and thus think that his Wudu' has been invalidated. (Using translation from Nasāʾī 134)   

أَنَّ رَسُولَ اللهِ ﷺ «كَانَ إِذَا تَوَضَّأَ أَخَذَ حَفْنَةً مِنْ مَاءٍ فَقَالَ بِهَا هَكَذَا وَوَصَفَ شُعْبَةُ نَضَحَ بِهِ فَرْجَهُ» فَذَكَرْتُهُ لِإِبْرَاهِيمَ فَأَعْجَبَهُ