Sunan Ibn Majah 355
Abu Sufyan said:
"Abu Ayyub Al-Ansari, Jabir bin 'Abdullah, and Anas bin Malik told me that when this Verse: "In it (the mosque) are men who love to clean and to purify themselves. And Allah loves those who make themselves clean and pure." was revealed, the Messenger of Allah said: 'O Ansar! Allah has praised you for your cleanliness. What is the nature of your cleanliness?' They said: 'We  perform ablution for prayer and we take bath to cleanse ourselves of impurity due to sexual activity, and we clean ourselves with water (after urinating). He said: 'This is what it is. So adhere to it.'"
حَدَّثَنَا هِشَامُ بْنُ عَمَّارٍ، حَدَّثَنَا صَدَقَةُ بْنُ خَالِدٍ، حَدَّثَنَا عُتْبَةُ بْنُ أَبِي حَكِيمٍ، حَدَّثَنِي طَلْحَةُ بْنُ نَافِعٍ أَبُو سُفْيَانَ، قَالَ حَدَّثَنِي أَبُو أَيُّوبَ الأَنْصَارِيُّ، وَجَابِرُ بْنُ عَبْدِ اللَّهِ، وَأَنَسُ بْنُ مَالِكٍ، أَنَّ هَذِهِ الآيَةَ، نَزَلَتْ ‏{فِيهِ رِجَالٌ يُحِبُّونَ أَنْ يَتَطَهَّرُوا وَاللَّهُ يُحِبُّ الْمُطَّهِّرِينَ}‏ قَالَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ ‏"‏ يَا مَعْشَرَ الأَنْصَارِ إِنَّ اللَّهَ قَدْ أَثْنَى عَلَيْكُمْ فِي الطُّهُورِ فَمَا طُهُورُكُمْ ‏"‏ ‏.‏ قَالُوا نَتَوَضَّأُ لِلصَّلاَةِ وَنَغْتَسِلُ مِنَ الْجَنَابَةِ وَنَسْتَنْجِي بِالْمَاءِ ‏.‏ قَالَ ‏"‏ هُوَ ذَلِكَ فَعَلَيْكُمُوهُ ‏"‏ ‏.‏