Sunan an-Nasa'i 132

أَخْبَرَنَا زِيَادُ بْنُ أَيُّوبَ، قَالَ حَدَّثَنَا ابْنُ عُلَيَّةَ، قَالَ حَدَّثَنَا أَيُّوبُ، عَنِ ابْنِ أَبِي مُلَيْكَةَ، عَنِ ابْنِ عَبَّاسٍ، أَنَّ رَسُولَ اللَّهِ صلى الله عليه وسلم خَرَجَ مِنَ الْخَلاَءِ فَقُرِّبَ إِلَيْهِ طَعَامٌ فَقَالُوا أَلاَ نَأْتِيكَ بِوَضُوءٍ فَقَالَ ‏ "‏ إِنَّمَا أُمِرْتُ بِالْوُضُوءِ إِذَا قُمْتُ إِلَى الصَّلاَةِ ‏"‏ ‏.‏

It was narrated from Ibn 'Abbas that the Messenger of Allah (ﷺ) came out from the toilet and food was brought to him. They said:"Shall we not bring water for Wudu'?" He said: "I have only been commanded to perform Wudu' when I want to pray

Reference

Sunan an-Nasa'i 132

In-book

Book 1, Hadith 133