It was narrated from Talhah bin 'Ubaidullah that:

a Bedouin came to the Messenger of Allah with unkempt hair and said: "O Allah has enjoined upon me of Salah." He said: "The five daily prayers, unless you do any more voluntarily." He said: "Tell me what Allah has enjoined upon me voluntarily." He said: "Tell me what Allah has enjoined upon me of fasting." He said: "Fasting the month of Ramadan, unless you do any more voluntarily." He said: "Tell me what Allah has enjoined upon me of Zakah." The Messenger of Allah told him of the laws of Islam, He said: "By the One Who has honored you, I will not do anything voluntarily, and I will not do anything voluntarily, and I will not do less than that which Allah has enjoined upon, me: The Messenger of Allah said: "He will succeed if he is sincere," or "He will enter Paradise if he is sincere."

أَخْبَرَنَا عَلِيُّ بْنُ حُجْرٍ، قَالَ حَدَّثَنَا إِسْمَاعِيلُ، - وَهُوَ ابْنُ جَعْفَرٍ - قَالَ حَدَّثَنَا أَبُو سُهَيْلٍ، عَنْ أَبِيهِ، عَنْ طَلْحَةَ بْنِ عُبَيْدِ اللَّهِ، أَنَّ أَعْرَابِيًّا، جَاءَ إِلَى رَسُولِ اللَّهِ ﷺ ثَائِرَ الرَّأْسِ فَقَالَ يَا رَسُولَ اللَّهِ أَخْبِرْنِي مَاذَا فَرَضَ اللَّهُ عَلَىَّ مِنَ الصَّلاَةِ قَالَ " الصَّلَوَاتُ الْخَمْسُ إِلاَّ أَنْ تَطَوَّعَ شَيْئًا " . قَالَ أَخْبِرْنِي بِمَا افْتَرَضَ اللَّهُ عَلَىَّ مِنَ الصِّيَامِ قَالَ " صِيَامُ شَهْرِ رَمَضَانَ إِلاَّ أَنْ تَطَوَّعَ شَيْئًا " . قَالَ أَخْبِرْنِي بِمَا افْتَرَضَ اللَّهُ عَلَىَّ مِنَ الزَّكَاةِ فَأَخْبَرَهُ رَسُولُ اللَّهِ ﷺ بِشَرَائِعِ الإِسْلاَمِ . فَقَالَ وَالَّذِي أَكْرَمَكَ لاَ أَتَطَوَّعُ شَيْئًا وَلاَ أَنْقُصُ مِمَّا فَرَضَ اللَّهُ عَلَىَّ شَيْئًا . فَقَالَ رَسُولُ اللَّهِ ﷺ " أَفْلَحَ إِنْ صَدَقَ " . أَوْ " دَخَلَ الْجَنَّةَ إِنْ صَدَقَ " .