Riyad us Saliheen: Hadith 166

Messenger of Allah (ﷺ) prohibited flicking pebbles by the index finger and the thumb; and he said, "It does not kill a game animal nor does it inflict wound on the enemy, but breaks the tooth and gorges the eye".

[Al-Bukhari and Muslim].

In another narration it is said: A close relative of 'Abdullah bin Mughaffal (May Allah be pleased with him) was hitting with pebbles using the index finger and the thumb; he said: "Messenger of Allah (ﷺ) has forbidden it saying that it does not kill the game". He repeated the act and Ibn Mughaffal said to him: "I told you that the Prophet (ﷺ) had prohibited it but you repeated it. I shall never talk to you."