Sahih Al Bukhari 1: Chapter 3, Hadith 85

(85) Whoever gave a religious verdict by beckoning or by nodding

حَدَّثَنَا الْمَكِّيُّ بْنُ إِبْرَاهِيمَ، ‏‏‏‏‏‏قَالَ:‏‏‏‏ أَخْبَرَنَا حَنْظَلَةُ بْنُ أَبِي سُفْيَانَ، ‏‏‏‏‏‏عَنْ سَالِمٍ، ‏‏‏‏‏‏قَالَ:‏‏‏‏ سَمِعْتُ أَبَا هُرَيْرَةَ، ‏‏‏‏‏‏عَنِ النَّبِيِّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ، ‏‏‏‏‏‏قَالَ:‏‏‏‏ "يُقْبَضُ الْعِلْمُ، ‏‏‏‏‏‏وَيَظْهَرُ الْجَهْلُ وَالْفِتَنُ، ‏‏‏‏‏‏وَيَكْثُرُ الْهَرْجُ، ‏‏‏‏‏‏قِيلَ:‏‏‏‏ يَا رَسُولَ اللَّهِ، ‏‏‏‏‏‏وَمَا الْهَرْجُ؟ فَقَالَ:‏‏‏‏ هَكَذَا بِيَدِهِ، ‏‏‏‏‏‏فَحَرَّفَهَا كَأَنَّه يُرِيدُ الْقَتْلَ".

SAHIH HADITH:

Narrated Abu Huraira: The Prophet 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 Apostle? He replied by beckoning with his hand indicating killing. (Fath-al-Bari Page 192, Vol. 1)

REFERENCE:

Sahih Al Bukhari 1: Chapter 3, Hadith 85