ENOfficial
Ibn 'Abbas reported: We were with the Messenger of Allah (ﷺ) and he had come out of the privy. Food was presented to him. It was said to him (by the Companions around him): Wouldn't you perform ablution? Upon this he said: Why, am I to say prayer that I should perform ablution?
Source: sunnah.com
Other translations
Arabic
وَحَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا سُفْيَانُ بْنُ عُيَيْنَةَ، عَنْ عَمْرٍو، عَنْ سَعِيدِ بْنِ الْحُوَيْرِثِ، سَمِعْتُ ابْنَ عَبَّاسٍ، يَقُولُ كُنَّا عِنْدَ النَّبِيِّ صلى الله عليه وسلم فَجَاءَ مِنَ الْغَائِطِ وَأُتِيَ بِطَعَامٍ فَقِيلَ لَهُ أَلاَ تَوَضَّأُ فَقَالَ " لِمَ أَأُصَلِّي فَأَتَوَضَّأَ " .
sunnah.com