Sahih al-Bukhari 85
Narrated Abu Huraira:
The Prophet (ﷺ) said, "(Religious) knowledge will be taken away (by the death of religious scholars) 
ignorance (in religion) and afflictions will appear; and Harj will increase." It was asked, "What is 
Harj, O Allah's Messenger (ﷺ)?" He replied by beckoning with his hand indicating "killing." (Fath-al-Bari 
Page 192, Vol. 1)
حَدَّثَنَا الْمَكِّيُّ بْنُ إِبْرَاهِيمَ، قَالَ أَخْبَرَنَا حَنْظَلَةُ بْنُ أَبِي سُفْيَانَ، عَنْ سَالِمٍ، قَالَ سَمِعْتُ أَبَا هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ ‏
"‏ يُقْبَضُ الْعِلْمُ، وَيَظْهَرُ الْجَهْلُ وَالْفِتَنُ، وَيَكْثُرُ الْهَرْجُ ‏"‏‏.‏ قِيلَ يَا رَسُولَ اللَّهِ وَمَا الْهَرْجُ فَقَالَ هَكَذَا بِيَدِهِ، فَحَرَّفَهَا، كَأَنَّهُ يُرِيدُ الْقَتْلَ‏.‏