كتاب الفتن
Afflictions and the End of the World
Chapter: Information about Ad-Dajjal
باب ذِكْرِ الدَّجَّالِ
Sahih al-Bukhari 7122

Narrated Al-Mughira bin Shu`ba:

Nobody asked the Prophet (ﷺ) as many questions as I asked regarding Ad-Dajjal. The Prophet (ﷺ) said to me, "What worries you about him?" I said, "Because the people say that he will have a mountain of bread and a river of water with him (i.e. he will have abundance of food and water)" The Prophet (ﷺ) said, "Nay, he is too mean to be allowed such a thing by Allah"' (but it is only to test mankind whether they believe in Allah or in Ad-Dajjal.)

حَدَّثَنَا مُسَدَّدٌ، حَدَّثَنَا يَحْيَى، حَدَّثَنَا إِسْمَاعِيلُ، حَدَّثَنِي قَيْسٌ، قَالَ قَالَ لِي الْمُغِيرَةُ بْنُ شُعْبَةَ مَا سَأَلَ أَحَدٌ النَّبِيَّ صلى الله عليه وسلم عَنِ الدَّجَّالِ مَا سَأَلْتُهُ وَإِنَّهُ قَالَ لِي ‏"‏ مَا يَضُرُّكَ مِنْهُ ‏"‏‏.‏ قُلْتُ لأَنَّهُمْ يَقُولُونَ إِنَّ مَعَهُ جَبَلَ خُبْزٍ وَنَهَرَ مَاءٍ‏.‏ قَالَ ‏"‏ هُوَ أَهْوَنُ عَلَى اللَّهِ مِنْ ذَلِكَ ‏"‏‏.‏
Reference : Sahih al-Bukhari 7122
In-book reference : Book 92, Hadith 69
USC-MSA web (English) reference : Vol. 9, Book 88, Hadith 238
  (deprecated numbering scheme)