(What is said regarding) the disappearance of the (religious) knowledge and the appearance of (religious) ignorance

Narrated Anas: Allah's Messenger (sallallahu 'alaihi wa sallam) 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.