Musannaf Ibn Abi Shayba 18:205

Abu Bakr narrated to us, he said: Abu Usama narrated to us, from Muhammad ibn ‘Amr, from ‘Umar ibn ‘Abd al-‘Aziz, he said regarding the tongue: The full blood money (diyah). And whatever is injured of the tongue, if it reaches the point of preventing speech, then in it is the full blood money.