Musannaf Ibn Abi Shayba 33:1349

Yazid ibn Harun narrated to us, he said: Al-Mas'udi informed us, from 'Awn ibn 'Abd Allah, that he used to say: "Behold, forbearance, modesty, and speechlessness—the speechlessness of the tongue, not the speechlessness of the heart—and understanding (fiqh) are from faith. They are among the things that decrease from the worldly life and increase in the Hereafter, and what they increase in the Hereafter is greater than what they decrease from the worldly life. Verily, obscenity, foulness, harshness, and eloquence (in a negative sense) are from hypocrisy. They are among the things that increase in the worldly life and decrease from the Hereafter, and what they decrease from the Hereafter is greater than what they increase in the worldly life."