Arabic text
عن سهل بن سعد رضي الله عنه عن رسول الله صلى الله عليه وسلم قال: «مَنْ يَضْمَنْ لِي مَا بَيْنَ لَحْيَيْهِ وَمَا بَيْنَ رِجْلَيْهِ أَضْمَنْ لَهُ الْجَنَّةَ».
Translation
Sahl ibn Sa‘d (may Allah be pleased with him) reported: The Messenger of Allah (may Allah’s peace and blessings be upon him) said: "Whoever gives me a guarantee to safeguard what is between his jaws and what is between his legs, I will guarantee him Paradise."
Explanation
The Prophet (may Allah's peace and blessings be upon him) informs us about two things, which if a Muslim observes, he will enter Paradise. First: protecting the tongue from saying things that displease Allah Almighty. Second: preserving the private parts from obscenity. This is because these two organs are often used in the perpetration of sins.
Source: HadeethEnc.com