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 ‏"‏‏.‏