Language:
كتاب العلم
3
Knowledge
(24)
Chapter: Whoever gave a religious verdict by beckoning or by nodding
(24)
باب مَنْ أَجَابَ الْفُتْيَا بِإِشَارَةِ الْيَدِ وَالرَّأْسِ

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.‏
Reference : Sahih al-Bukhari 85
In-book reference : Book 3, Hadith 27
USC-MSA web (English) reference : Vol. 1, Book 3, Hadith 85
  (deprecated numbering scheme)