Safeguarding the Tongue
A reminder filled with narrations from the Prophet and his Companions concerning the grave sins of the tongue.
There is not a part of the body except that it complains to Allāh because of the tongue - due to its haste/rashness.
Rasūl Allāh (ṣallallāhu ʿalayhi wa-sallam) said: When the son of Ādam gets up in the morning all the limbs humble themselves before the tongue and say: Have taqwa of Allāh for our sake, for we are dependent on you, If you are straight/upright, we are straight and If you are crooked, we are crooked.
Ḥasan - narrated by al-Tirmidhī, lbn Khuzaymah and Ibn Hibbān from Abū Saʿīd al-Khudrī marfūʿān and authenticated by al-Albānī in (Ṣaḥīḥ al-Jāmiʿ) 
Rasūl Allāh (ṣallallāhu ʿalayhi wa-sallam)said: If anyone guarantees me what s between his jaws and between his legs, I shall guarantee him Jannah.
Ṣaḥīḥ - narrated by al-Bukhārī from Sahl lbn Saʿd marfūʿ'aan
He (ṣallallāhu ʿalayhi wa-sallam) was asked as to what thing brings people into al-Jannah the most and he said: Taqwá of Allāh and good character. Then he was asked as to what thing brings people into the Fire the most and he said : The mouth and the private-parts.
Ḥasan lsnād -narrated by al-Tirmidhī [20041. Ibn Mājah [42461, Aḥmad 12/29 1, 392, 4421, Ibn Hibbān [ 1923 - al-Mawārid], al- Baghawī In (Shaḥ al-Sunnah) 113179-801 and others, and It was authenticated by al Albānī in (al-Ṣaḥihah)  - from Abū Hurayrah marfūʿān.
In a lengthy ḥadīth, Rasūl Allāh (ṣallallāhu ʿalayhi wa-sallam) said:
Shall I not tell you about the peak of the matter, Its pillar and Its top-most part. I said: Yes O Rasūl Allāh. He said: The peak of the matter Is Islām,, the pillar Is ṣalāh; and Its top-most part is Jihād (to struggle against one's own self). Then he said: Shall I not tell you of the controlling of all that? I said: Yes O Rasūl Allāh, and he took hold of his tongue and said: Restrain this. I said: O Nabī of Allāh, will what we say be held against us ? He said : May your mother be bereaved of you, O Muʿādh ! Is there anything which topples people on their faces - or he said : On their noses - Into Hell-Fire other than the harvests of their tongues
Ṣaḥīḥ - narrated by al-Tirmidhī 121 101, Ibn Mājah (39731 and Aḥmad 15/23 11 from Muʿādh, and the isnād is ḥasan as al Albānī says in (al-'Irwá') 
O Rasūl Allāh! Inform me of something which I may hold fast to ? He (ṣallallāhu ʿalayhi wa-sallam) said:
Say ! My Rabb Is Allāh and thereafter be upright I said : 0 Rasūl Allāh I What is the thing that you fear most for me ? He took hold of his tongue and said : This !
Ṣaḥīḥ - narrated by at- Tirmidhī 11965]. Ibn Mājah [39721 and Aḥmad [3/4131 from Sufyān ibn ʿAbdullāh al-Thaqafī.
Rasūl Allāh (ṣallallāhu ʿalayhi wa-sallam) said: Most of the sins of the Children of Ādam are from his tongue.
Ṣaḥīḥ - narrated by at-Ṭabarānī 13/87/1-21, Abū'sh - Shaykh 12/101 and lbn 'ʿAsākir (11389/151 and authenticated in (as-Saheeah) 
Rasūl Allāh (ṣallallāhu ʿalayhi wa-sallam) said: There Is not a part of the body except that It complains to Allāh because of the tongue - due to its haste / rashness.
Ṣaḥīḥ - narrated by Abū Yaʿlā (Musnad) [1/41. Ibn al-Sunnī [71. Ibn Abī' al-Dunyā in ((al-Warr)) [Q.2/1651, Abū Nu'aym [209/1-2] and al-Bayḥaqī in (al-Shub) [2/65/91 see al-Albānī's (al-Ṣaḥihah) .
The wounds of a sword may heal one day, But the wounds of the tongue - they never may.