When we talk about tongue and the ability to speak, it is necessary to speak about things that corrupt the tongue, because there is a cause of corruption for everything and the tongue is not an exception to this. Many causes have been cited in this regard:
1-Over talking: it is one of the bad characteristics because possible mistake in talkative persons is much more than taciturn persons. For this reason, The Noble Prophet said: “Blessed be the one who restrains his tongue from excessive speech.” (Al-Mahajjah al-Bayda, v.5, p.200)
2- Swearing: One who swears in fact, harm to the character of others and such practice is certainly forbidden. Hence Prophet Muhammad (Peace be upon Him and His progeny) has said: “Heaven is forbidden to whoever is used to swearing. He/she cannot enter it.” (Ibid, p.215)
3- Joking Around: “abstain from excessive joking around with your brethren.” (Ibid, p.231)
Of course, good jokes are okay as The Prophet told some nice jokes. For example One day an old lady went to see the Prophet . The Prophet said: “An old lady does not go to Heaven.” The old lady started to cry. Then the Prophet said: “On that day you will not be old. You will be young. God has said the following in the Holy Qur’an:” “We have created (their Companions) of special creation, and made them virgin – pure.” (56:35-36)
However If we’re not careful with our speech, it may harm us and others.