Sahih al-Bukhari 6474
Sahih al-Bukhari · Book 81: To make the Heart Tender (Ar-Riqaq) · To protect one's tongue
Narrated Sahl bin Sa`d:
حَدَّثَنَا مُحَمَّدُ بْنُ أَبِي بَكْرٍ الْمُقَدَّمِيُّ ، حَدَّثَنَا عُمَرُ بْنُ عَلِيٍّ ، سَمِعَ أَبَا حَازِمٍ ، عَنْ سَهْلِ بْنِ سَعْدٍ ، عَنْ رَسُولِ اللَّهِ صلى الله عليه وسلم قَالَ " مَنْ يَضْمَنْ لِي مَا بَيْنَ لَحْيَيْهِ وَمَا بَيْنَ رِجْلَيْهِ أَضْمَنْ لَهُ الْجَنَّةَ " .
Allah's Messenger (ﷺ) said, "Whoever can guarantee (the chastity of) what is between his two jaw-bones and what is between his two legs (i.e. his tongue and his private parts), I guarantee Paradise for him."