"Successful are the believers, who are humble in their prayers, and who turn away from pointless talk, [23:1-3] and: Those who do not bear witness to what is false, but when they pass by pointless talk, pass by with dignity, [25:72] and: When they hear pointless talk, they turn away from it." [28:55]
“Pointless talk” [laghw] is speech which is futile and irrelevant, and bears no relation to any true purpose. It brings no benefit to the one who utters it, and may well bring him misfortune instead.
Hazrat Ali (ra) related that the Messenger of Allah (sallallahu `alayhi wa sallam) said, “It is part of a man’s sound practice of Islam that he leave alone that which is of no concern to him.” [At-Tirmidhi, Ibn Majah]
Dhu’l-Nun said, “Whoever loves Allah lives truly, and whoever inclines to anything else damages his mind. A foolish man comes and goes, paying attention to what is nothing, while the intelligent man inspects his own thoughts scrupulously.”