Feridüddin Attar (quddisa sirruhu), the renowned 12th-century Sufi scholar in his book titled Pendname declared thusly:
Wise is he who is eternally grateful to Allah (subhanahu wa taala), and whose will outstrips his nafs,the source of his worldly desires. O young man! He who overcomes his anger will surely attain salvation in this world. Foolish among all men is he who pursues his every desire, his every impulse. How feeble-minded, for he presumes that Allah (subhanahu wa taala) will no doubt absolve him of his misdeeds.
O son! Difficult as it may be, there is no more admirable status than that of the dervish. Among the wise is he who subjugates the nafs, which advocates wanton desires and evil deeds. Discipline your desires through abstinence and temperance so it will not cause you further deprivation.
Recognize that all of creation is in a state of slumber. The deceased will depart into the hereafter awoken from their blind slumber. Forgive those who have wronged you, accept graciously their trespasses and contrition. Refrain from harboring resentment toward them to attain Allah’s true absolution. Allah (subhanahu wa taala) loves not those who intentionally harm people, for the faithful do not harbor such morals.
Whosoever breaks one's heart through willful oppression will indeed open those very wounds within himself. The suffering for those who relish hurting people is one of great lament and weeping. O son! Be not of those who turn away from their Lord by mistreating people. Do not hurt the feelings of those around you, otherwise you will only be hurting yourself.
Honor people with kindness if you want to be respected. If you lack the capacity for good, at least refrain from doing harm so you do not bring immeasurable harm to yourself. One who is unable to refrain from slander will in no way obtain salvation in the hereafter. Safeguard your tongue from slander so you don’t have your hands and feet bound by chains on the Day of Judgment.
O my brother! If you want to reach your Creator, then do not speak save what the Almighty commands of you. If you have any awareness of your Creator who is eternally alive and does not die, then seal your mouth shut.
O son! If you want to be as those who seek true salvation then heed the advice and listen in silent contemplation. One who talks too much will no doubt darken their heart and afflict their soul. The virtue of the wise is to remain silent and as for the ignorant, it is to forget. It is obligatory to remain silent instead of lying and gossiping. Foolish are those who persist in such willful actions and insist on speaking in such situations.
My brother! Speak naught but only praises for Allah (subhanahu wa taala) and do not use the words of the Almighty to loot and plunder. One who is so inclined to idle talk will no doubt have all of his possessions plundered as well. Excessive idle talk will extinguish the heart even if the words are subtle.
O mankind who is trying to talk with embellishment, you are only opening wounds on your heart. Go and imprison your tongue within your mouth and expect no gain whatsoever from the rest of creation. He who sees his own flaws and imperfections will no doubt find the strength within his soul.