The Prophet ﷺ forbade the throwing of stones (with the thumb and the index or middle finger), and said "It neither hunts a game nor kills (or hurts) an enemy, but it gouges out an eye or breaks a tooth."  

نَهَى النَّبِيُّ ﷺ عَنِ الْخَذْفِ وَقَالَ إِنَّهُ لاَ يَقْتُلُ الصَّيْدَ وَلاَ يَنْكَأُ الْعَدُوَّ وَإِنَّهُ يَفْقَأُ الْعَيْنَ وَيَكْسِرُ السِّنَّ