What did al-Nawawi say about guarding the tongue?

"And the Qur'an is the speech of Allah; from Him it began, without modality, as a saying, and He sent it down upon His Messenger as revelation, and the believers testified to that as true, and they were certain that it is the speech of Allah Most High in very truth, not created as the speech of created beings is created. So whoever hears it and claims that it is the speech of a human being has disbelieved. And Allah has censured him and reproached him and threatened him with Saqar, where He said, Most High: Him shall I fling unto the burning. So when Allah threatened with Saqar the one who said: This is naught else than speech of mortal man, we knew and were certain that it is the speech of the Creator of mankind, and it does not resemble the speech of mankind."

"Rather, they only experience life to feel pain. The point is that when a person is in distress or calamity, their heart, tongue, and limbs fail them in what would be of most benefit to them. Their heart does not incline towards reliance on Allah, returning to Him, focusing on Him, supplicating, and humbling themselves before Him. Their tongue does not comply with remembrance, and even if they mention Allah by tongue, they do not unite their heart with their tongue, so that the remembrance becomes effective. Nor do their heart and tongue focus on the One Remembered. Instead, if they remember or supplicate, they"

"about what he feared from the people of Pharaoh concerning the slain man and the impediment of his speech, for there was an impediment on his tongue that prevented him from much speech. He asked his Lord to support him with his brother Aaron, to be an aid for him, to speak on his behalf concerning much that his tongue could not articulate. God Almighty granted him his request, loosened a knot from his tongue, and God revealed to Aaron and commanded him to meet with him. Moses set out with his staff until he met Aaron, and together they proceeded to Pharaoh. They stood at his gate for a while before finally"

"victors. In Surat Taha Allah says go to Pharaoh indeed he has transgressed. Moses said my lord open for me my chest and ease for me my task and untie the knot from my tongue that they may understand my speech. It is said that he had a lisp in his tongue because of the coal he placed on it. Pharaoh wanted to test Moses's wit when as a child Moses grabbed his beard prompting Pharaoh to consider killing him. Asiyah feared for him and said he is just a child. To test him Pharaoh placed a date and a hot coal before him. Moses reached for the date but an angel guided his hand to the coal which he then put on his tongue causing"

"The second is guarding the tongue from idle chatter, lying, backbiting, gossiping, foul language, harshness, arguments, and disputes, instead obliging oneself to silence and occupying it with the remembrance of Allah and recitation of the Quran. This is the fasting of the tongue. Sufyan said that backbiting ruins the fast. Moreover, it is narrated that Mujahid said: "Two traits ruin fasting: backbiting and lying.""

"This is among the noblest types of remembrance. There are five types of remembrance. Sometimes it occurs through both the heart and tongue together, which is the best form. Other times it is through the heart alone, which holds the second rank. Lastly, it can be through the tongue alone, which is the third rank. The best remembrance is when the heart and tongue are in harmony. Chapter The Remembrance of Allah is Superior to Supplication Indeed, the remembrance of the heart alone is superior to the remembrance of the tongue alone. This is because the remembrance of the heart leads to knowledge, stirs love, arouses modesty, inspires fear, calls to vigilance,"

"A benefit: among those who practice remembrance are some who begin with the remembrance of the tongue, even while heedless, and then keep at it until the heart is present, so that the two go together in the remembrance. Others see it otherwise and will not begin while heedless; rather they grow still until the heart is present, then set out in remembrance with the heart, and when it grows strong it draws the tongue along after it, so that the two go together. The first transfers the remembrance from his tongue to his heart; the second transfers it from his heart to his tongue without his heart ever being empty of it."

"peace be upon them, "And We granted them a high tongue of truth." The intended meaning of "tongue" here is good praise. Since truth is with the tongue, اللّٰه set the tongues of His servants free to praise the truthful one, as a fitting reward, and expressed it through him. The term "tongue" can have three meanings. First, it can refer to language, as in اللّٰه's words: "And We did not send any messenger except [speaking] in the language of his people to clarify for them," from سُورَة إِبْرَاهِيم, and "And the diversity of your tongues and colors," from سُورَة الرُّوم."

"When asked, he said no. The Prophet, peace be upon him, concluded to the man, "Rise, for he may be better than you." Treatment to Prevent the Tongue from Backbiting Know that the remedy for all evil traits is found in the combination of knowledge and action. The treatment of each ailment lies in countering its cause. Let us investigate its cause, and the remedy for restraining the tongue from backbiting is twofold: one general and one specific."

"His attributes do not resemble those of creatures, just as His essence does not resemble the essences of creatures. Speech: He is a speaker, commanding, prohibiting, promising, and warning with eternal speech inherent to His self, which does not resemble the speech of creatures. It is not a sound that emerges from the movement of air or the clashing of bodies, nor a letter that ceases with the closing of lips or movement of a tongue."