Sunan an-Nasa'i, Volume 1, Book 5, Hadith 459 (DarusSalam) ⓘ

It was narrated from Abu Suhail, from his fatehr, that he heard Talhah bin 'Ubaidullah say: "A man from the people of Najd came to the Messenger of Allah with unkempt hair. We could hear him talking loudly but we could not understand what he was saying until he came closer. He was asking about Islam. The Messenger of Allah said to him: 'Five prayers each day and night.' He said: 'Do I have to do anything else' He said: 'No, unless you do it voluntarily.' He said: 'And fasting the month of Ramadan.' He said: 'Do I have to do anything else?' He said: 'No, unless you do it voluntarily.' And the Messenger of Allah mentioned Zakah to him, and he said: 'Do I have to do anything else?' He said: 'No, unless you do it voluntarily.' The man left saying: 'By Allah, I will not do any more than this or any less.' The Messenger of Allah said: 'He will achieve salvation, if he is speaking the truth.'"

أَخْبَرَنَا قُتَيْبَةُ، عَنْ مَالِكِ بْنِ أَنَسٍ، عَنْ أَبِي سُهَيْلٍ، عَنْ أَبِيهِ، أَنَّهُ سَمِعَ طَلْحَةَ بْنَ عُبَيْدِ اللَّهِ، يَقُولُ جَاءَ رَجُلٌ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم مِنْ أَهْلِ نَجْدٍ ثَائِرَ الرَّأْسِ نَسْمَعُ دَوِيَّ صَوْتِهِ وَلاَ نَفْهَمُ مَا يَقُولُ حَتَّى دَنَا فَإِذَا هُوَ يَسْأَلُ عَنِ الإِسْلاَمِ فَقَالَ لَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ خَمْسُ صَلَوَاتٍ فِي الْيَوْمِ وَاللَّيْلَةِ ‏"‏ ‏.‏ قَالَ هَلْ عَلَىَّ غَيْرُهُنَّ قَالَ ‏"‏ لاَ إِلاَّ أَنْ تَطَّوَّعَ ‏"‏ ‏.‏ قَالَ ‏"‏ وَصِيَامُ شَهْرِ رَمَضَانَ ‏"‏ ‏.‏ قَالَ هَلْ عَلَىَّ غَيْرُهُ قَالَ ‏"‏ لاَ إِلاَّ أَنْ تَطَّوَّعَ ‏"‏ ‏.‏ وَذَكَرَ لَهُ رَسُولُ اللَّهِ صلى الله عليه وسلم الزَّكَاةَ قَالَ هَلْ عَلَىَّ غَيْرُهَا قَالَ ‏"‏ لاَ إِلاَّ أَنْ تَطَّوَّعَ ‏"‏ ‏.‏ فَأَدْبَرَ الرَّجُلُ وَهُوَ يَقُولُ وَاللَّهِ لاَ أَزِيدُ عَلَى هَذَا وَلاَ أَنْقُصُ مِنْهُ ‏.‏ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏"‏ أَفْلَحَ إِنْ صَدَقَ ‏"‏ ‏.‏