It neither inflicts defeat to the enemy nor kills the game but breaks the tooth and puts the eye out. This hadith has been transmitted on the authority of Ibn Mahdi with a slight variation of wording.
نَهَى رَسُولُ اللَّهِ ﷺ عَنِ الْخَذْفِ قَالَ ابْنُ جَعْفَرٍ فِي حَدِيثِهِ وَقَالَ إِنَّهُ لاَ يَنْكَأُ الْعَدُوَّ وَلاَ يَقْتُلُ الصَّيْدَ وَلَكِنَّهُ يَكْسِرُ السِّنَّ وَيَفْقَأُ الْعَيْنَ وَقَالَ ابْنُ مَهْدِيٍّ إِنَّهَا لاَ تَنْكَأُ الْعَدُوَّ وَلَمْ يَذْكُرْ تَفْقَأُ الْعَيْنَ
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
“The Prophet ﷺ forbade throwing small pebbles and said: ‘They do not kill any game nor hurt the enemy, but they can break a tooth or put out an eye.’” He did it again, and he (‘Abdullah) said: “I tell you that the Prophet ﷺ forbade that and then you go and do it again? I will never speak to you again.”
وَقَالَ إِنَّ النَّبِيَّ ﷺ نَهَى عَنِ الْخَذْفِ وَقَالَ إِنَّهَا لاَ تَصِيدُ صَيْدًا وَلاَ تَنْكَأُ عَدُوًّا وَلَكِنَّهَا تَكْسِرُ السِّنَّ وَتَفْقَأُ الْعَيْنَ قَالَ فَعَادَ فَقَالَ أُحَدِّثُكَ أَنَّ النَّبِيَّ ﷺ نَهَى عَنْهُ ثُمَّ عُدْتَ لاَ أُكَلِّمُكَ أَبَدًا
The Messenger of Allah ﷺ prohibited throwing pebbles (in sport) saying : game is not caught by such means. Neither is an enemy injured, but it may sometimes put out an eye or break a tooth. (Using translation from Abū Dāʾūd 5270)
أَنَّ رَسُولَ اللهِ ﷺ نَهَى عَنِ الْخَذْفِ وَقَالَ إِنَّهُ لَا يَنْكَأُ عَدُوًّا وَلَا يَصِيدُ صَيْدًا وَلَكِنَّهُ يَكْسِرُ السِّنَّ وَيَفْقَأُ الْعَيْنَ