Language:
كتاب العلم
3  
Knowledge
(21)
Chapter: (What is said regarding) the disappearance of the (religious) knowledge and the appearance of (religious) ignorance
(21)
باب رَفْعِ الْعِلْمِ وَظُهُورِ الْجَهْلِ
Sahih al-Bukhari 80

Narrated Anas:

Allah's Messenger (ﷺ) said, "From among the portents of the Hour are (the following): -1. Religious knowledge will be taken away (by the death of Religious learned men). -2. (Religious) ignorance will prevail. -3. Drinking of Alcoholic drinks (will be very common). -4. There will be prevalence of open illegal sexual intercourse.

حَدَّثَنَا عِمْرَانُ بْنُ مَيْسَرَةَ، قَالَ حَدَّثَنَا عَبْدُ الْوَارِثِ، عَنْ أَبِي التَّيَّاحِ، عَنْ أَنَسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ إِنَّ مِنْ أَشْرَاطِ السَّاعَةِ أَنْ يُرْفَعَ الْعِلْمُ، وَيَثْبُتَ الْجَهْلُ، وَيُشْرَبَ الْخَمْرُ، وَيَظْهَرَ الزِّنَا ‏"‏‏.‏
Reference : Sahih al-Bukhari 80
In-book reference : Book 3, Hadith 22
USC-MSA web (English) reference : Vol. 1, Book 3, Hadith 80
  (deprecated numbering scheme)