Hadith 29, 40 Hadith an-Nawawi
On the authority of Muadh bin Jabal (may Allah be pleased with him) who said:
I said, “O Messenger of Allah, tell me of an act which will take me into Paradise and will keep me away from the Hellfire.” He (peace and blessings of Allah be upon him) said, “You have asked me about a great matter, yet it is easy for him for whom Allah makes it easy: worship Allah, without associating any partners with Him; establish the prayer; pay the zakat; fast in Ramadhan; and make the pilgrimage to the House.”

Then he (peace and blessings of Allah be upon him) said, “Shall I not guide you towards the means of goodness? Fasting is a shield; charity wipes away sin as water extinguishes fire; and the praying of a man in the depths of the night.” Then he (peace and blessings of Allah be upon him) recited: “[Those] who forsake their beds, to invoke their Lord in fear and hope, and they spend (charity in Allah’s cause) out of what We have bestowed on them. No person knows what is kept hidden for them of joy as a reward for what they used to do.” [as-Sajdah, 16-17]

Then he (peace and blessings of Allah be upon him) said, “Shall I not inform you of the head of the matter, its pillar and its peak?” I said, “Yes, O Messenger of Allah.” He (peace and blessings of Allah be upon him) said, “The head of the matter is Islam, its pillar is the prayer and its peak is jihad.” Then he (peace and blessings of Allah be upon him) said, “Shall I not tell you of the foundation of all of that?” I said, “Yes, O Messenger of Allah.” So he took hold of his tongue and said, “Restrain this.”

I said, “O Prophet of Allah, will we be taken to account for what we say with it?” He (peace and blessings of Allah be upon him) said, “May your mother be bereaved of you, O Muadh! Is there anything that throws people into the Hellfire upon their faces — or: on their noses — except the harvests of their tongues?”

It was related by at-Tirmidhi, who said it was a good and sound hadeeth.
عَنْ مُعَاذِ بْنِ جَبَلٍ رَضِيَ اللهُ عَنْهُ قَالَ: قُلْت يَا رَسُولَ اللَّهِ! أَخْبِرْنِي بِعَمَلٍ يُدْخِلُنِي الْجَنَّةَ وَيُبَاعِدْنِي مِنْ النَّارِ، قَالَ: "لَقَدْ سَأَلْت عَنْ عَظِيمٍ، وَإِنَّهُ لَيَسِيرٌ عَلَى مَنْ يَسَّرَهُ اللَّهُ عَلَيْهِ: تَعْبُدُ اللَّهَ لَا تُشْرِكْ بِهِ شَيْئًا، وَتُقِيمُ الصَّلَاةَ، وَتُؤْتِي الزَّكَاةَ، وَتَصُومُ رَمَضَانَ، وَتَحُجُّ الْبَيْتَ، ثُمَّ قَالَ: أَلَا أَدُلُّك عَلَى أَبْوَابِ الْخَيْرِ؟ الصَّوْمُ جُنَّةٌ، وَالصَّدَقَةُ تُطْفِئُ الْخَطِيئَةَ كَمَا يُطْفِئُ الْمَاءُ النَّارَ، وَصَلَاةُ الرَّجُلِ فِي جَوْفِ اللَّيْلِ، ثُمَّ تَلَا: " تَتَجَافَى جُنُوبُهُمْ عَنِ الْمَضَاجِعِ " حَتَّى بَلَغَ "يَعْمَلُونَ"،[ 32 سورة السجدة / الأيتان : 16 و 17 ] ثُمَّ قَالَ: أَلَا أُخْبِرُك بِرَأْسِ الْأَمْرِ وَعَمُودِهِ وَذُرْوَةِ سَنَامِهِ؟ قُلْت: بَلَى يَا رَسُولَ اللَّهِ. قَالَ: رَأْسُ الْأَمْرِ الْإِسْلَامُ، وَعَمُودُهُ الصَّلَاةُ، وَذُرْوَةُ سَنَامِهِ الْجِهَادُ، ثُمَّ قَالَ: أَلَا أُخْبِرُك بِمَلَاكِ ذَلِكَ كُلِّهِ؟ فقُلْت: بَلَى يَا رَسُولَ اللَّهِ ! فَأَخَذَ بِلِسَانِهِ وَقَالَ: كُفَّ عَلَيْك هَذَا. قُلْت: يَا نَبِيَّ اللَّهِ وَإِنَّا لَمُؤَاخَذُونَ بِمَا نَتَكَلَّمُ بِهِ؟ فَقَالَ: ثَكِلَتْك أُمُّك وَهَلْ يَكُبُّ النَّاسَ عَلَى وُجُوهِهِمْ -أَوْ قَالَ عَلَى مَنَاخِرِهِمْ- إلَّا حَصَائِدُ أَلْسِنَتِهِمْ؟!" . 
رَوَاهُ التِّرْمِذِيُّ [رقم:2616] وَقَالَ: حَدِيثٌ حَسَنٌ صَحِيحٌ.