A bedouin with unkempt hair came to Messenger of Allah ﷺ and said, "O Messenger of Allah ﷺ! Inform me what Allah has made compulsory for me as regards the prayers." He replied: "You have to offer perfectly the five compulsory prayers in a day and night (24 hours), unless you want to pray Nawafil." The bedouin further asked, "Inform me what Allah has made compulsory for me as regards fasting." He replied, "You have to fast during the whole month of Ramadan, unless you want to fast more as Nawafil." The bedouin further asked, "Tell me how much Zakat Allah has enjoined on me." Thus, Messenger of Allah ﷺ informed him about all the rules (i.e. fundamentals) of Islam. The bedouin then said, "By Him Who has honored you, I will neither perform any Nawafil nor will I decrease what Allah has enjoined on me. Messenger of Allah ﷺ said, "If he is saying the truth, he will succeed (or he will be granted Paradise). (Using translation from Bukhārī 1891)   

أَنَّ أَعْرَابِيًّا جَاءَ إِلَى رَسُولِ اللهِ ﷺ ثَائِرَ الرَّأْسِ فَقَالَ يَا رَسُولَ اللهِ أَخْبِرْنِي مَاذَا فَرَضَ اللهُ عَلَيَّ مِنَ الصَّلَاةِ فَقَالَ الصَّلَوَاتُ الْخَمْسُ إِلَّا أَنْ تَطَوَّعَ شَيْئًا فَقَالَ أَخْبِرْنِي مَا فَرَضَ اللهُ عَلَيَّ مِنَ الصِّيَامِ؟ فَقَالَ صِيَامُ شَهْرِ رَمَضَانَ إِلَّا أَنْ تَتَطَوَّعَ شَيْئًا فَقَالَ أَخْبِرْنِي مَاذَا فَرَضَ اللهُ عَلَيَّ مِنَ الزَّكَاةِ؟ قَالَ فَأَخْبَرَهُ يَعْنِي رَسُولَ اللهِ ﷺ بِشَرَائِعِ الْإِسْلَامِ فَقَالَ وَالَّذِي أَكْرَمَكَ لَا أَتَطَوَّعُ شَيْئًا وَلَا أَنْقُصُ مِمَّا فَرَضَ اللهُ عَلَيَّ شَيْئًا فَقَالَ رَسُولُ اللهِ ﷺ أَفْلَحَ وَأَبِيهِ إِنْ صَدَقَ دَخَلَ الْجَنَّةَ وَاللهِ إِنْ صَدَقَ