Sunan Ibn Majah #327 · The Book of Purification and its Sunnah

Sunan Ibn MajahIt was narrated that 'Aishah said
Sunan Ibn Majah · Book 1 · The Book of Purification and its Sunnah
Sunan Ibn Majah · كتاب 1 · كتاب الطهارة وسننها
"The Prophet went out to urinate, and 'Umar followed him with water. He said: 'What is this, O 'Umar?' He said: 'Water.' He said: 'I have not been commanded to perform ablution every time I urinate. If I did that it would have become a Sunnah
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا أَبُو أُسَامَةَ، عَنْ عَبْدِ اللَّهِ بْنِ يَحْيَى التَّوْأَمِ، عَنِ ابْنِ أَبِي مُلَيْكَةَ، عَنْ أُمِّهِ، عَنْ عَائِشَةَ، قَالَتِ انْطَلَقَ النَّبِيُّ ـ صلى الله عليه وسلم ـ يَبُولُ فَاتَّبَعَهُ عُمَرُ بِمَاءٍ فَقَالَ ‏
"‏ مَا هَذَا يَا عُمَرُ ‏"‏ ‏.‏ قَالَ مَاءٌ ‏.‏ قَالَ ‏"‏ مَا أُمِرْتُ كُلَّمَا بُلْتُ أَنْ أَتَوَضَّأَ وَلَوْ فَعَلْتُ لَكَانَتْ سُنَّةً ‏"‏ ‏.‏
Reference : Sunan Ibn Majah 327In-book reference : Book 1, Hadith 61