From Sahih Bukhari (Hadith 81):
Narrated Anas:I will narrate to you a Hadith and none other than I will tell you about after it. I heard Allah's Messenger (ﷺ) saying: From among the portents of the Hour are (the following): -1. Religious knowledge will decrease (by the death of religious learned men). -2. Religious ignorance will prevail. -3. There will be prevalence of open illegal sexual intercourse. -4. Women will increase in number and men will decrease in number so much so that fifty women will be looked after by one man
Reference: Bukhari 81