Who said the line: "Let your tongue not mention the faults of another"?

The aforementioned verse is attributed to Imam Al-Shafi'i and is found in his diwan, where he says: "If you desire a life of safety, and a protected religion and honor, then do not mention the faults of people, for you possess faults and people have tongues. And if your eyes see faults, then leave them and say to people: 'They have eyes.' And associate with kindness, forgive those who wronged you, and defend with that which is better."

Also among Al-Shafi'i's sayings about the tongue is: "Guard your tongue, O human, lest it sting you, for it is a snake. How many in the graves are victims of their tongues, whose peers feared meeting them."

The seriousness of the tongue is further emphasized by the words of Allah Almighty: "On the Day when their tongues, their hands, and their feet will bear witness against them as to what they used to do." (An-Nur:24), and the saying of the Prophet, peace and blessings be upon him: "Will anything cast people into the Hellfire on their faces—or he said: on their nostrils—except the harvests of their tongues?"