From the route of Mu^adh bin Jabal, may Allah accept his deeds, who said: I said: O Messenger of Allah inform me about a deed that makes me enter Paradise and keeps me away from Hellfire.
The Prophet said, <<You have asked about a great matter which is easy for the one whom Allah willed to make it easy for him. Worship Allah and do not associate anything with Him. Perform the prayers. Pay Zakat. Fast Ramadan and offer pilgrimage to the sacred house.>>
Thereafter the Prophet said, <<Should I guide you to the ports of goodness? They are: Fasting and which is like shielding equipment, charity and it puts out the sin as the water extinguishes the fire and the prayer of one in the middle of the night.>>
Then he recited:
{ تَتَجَافَى جُنُوبُهُمْ عَنِ الْمَضَاجِعِ يَدْعُونَ رَبَّهُمْ خَوْفًا وَطَمَعًا وَمِمَّا رَزَقْنَاهُمْ يُنفِقُونَ}
{َلا تَعْلَمُ نَفْسٌ مَّا أُخْفِيَ لَهُم مِّن قُرَّةِ أَعْيُنٍ جَزَاء بِمَا كَانُوا يَعْمَلُون }
Which means: [Their sides depart their beds and they make supplication to their Lord in fear and hopefullness, and they spend for the sake of Allah out of the sustenance that we Provided for them. No soul shall come to grips with the delightful enjoyments We have reserved for them as a reward for their good doings.]
Then the Prophet said, <<Do not you want me to tell you about the head, backbone and apex of all of that?>> I said: Yes indeed, O Messenger of Allah. He said:
<<The head of all of that is Islam and its backbone is the prayers and the apex of it is to struggle for the sake of Allah.>> Then he said: <<Do not you want me to tell you about what makes all of that sound and acceptable?>>
I said: Yes indeed O Prophet of Allah.
He held his tongue and said: <<Protect yourself from this.>>
I said: O Prophet of Allah are we accountable for what we say?
The Prophet said, <<Alas! Is there anything but the tongue that makes people drop on their faces (or he said: their noses) in hell fire?>>
Narrated by at-Tirmidhiyy and he said this Hadith is Hasan Sahih.