Al-An'aam 6:153

Imam Ahmad, Ibn Majah, in the Book of the Sunnah in his Sunan, and Al-Bazzar collected this Hadith. Ibn Jarir recorded that a man asked Ibn Mas`ud, "What is As-Sirat Al-Mustaqim (the straight path)" Ibn Mas`ud replied, "Muhammad ﷺ left us at its lower end and its other end is in Paradise. To the right of this Path are other paths, and to the left of it are other paths, and there are men (on these paths) calling those who pass by them. Whoever goes on the other paths will end up in the Fire. Whoever takes the Straight Path, will end up in Paradise." Ibn Mas`ud then recited the Ayah;

وَأَنَّ هَـذَا صِرَطِي مُسْتَقِيمًا فَاتَّبِعُوهُ وَلاَ تَتَّبِعُواْ السُّبُلَ فَتَفَرَّقَ بِكُمْ عَن سَبِيلِهِ

(And verily, this is My straight path, so follow it, and follow not (other) paths, for they will separate you away from His path.)'" Imam Ahmad recorded that, An-Nawwas bin Sam`an said that the Messenger of Allah ﷺ said,

«ضَرَبَ اللهُ مَثَلًا صِرَاطًا مُسْتَقِيمًا، وَعَنْ جَنْبَي الصِّرَاطِ سُورَانِ فِيهِمَا أَبْوَابٌ مُفَتَّحَةٌ، وَعَلَى الْأَبْوَابِ سُتُورٌ مُرْخَاةٌ وَعَلَى بَابِ الصِّرَاطِ دَاعٍ يَدْعُو: يَا أَيَّهَا النَّاسُ هَلُمُّوا ادْخُلُوا الصِّرَاطَ الْمُسْتَقِيمَ جَمِيعًا وَلَا تَفَرَّقُوا وَدَاعٍ يَدْعُو مِنْ فَوْقِ الصِّرَاطِ فَإِذَا أَرَادَ الِإنْسَانُ أَنْ يَفْتَحَ شَيْئًا مِنْ تِلْكَ الْأَبْوَابِ قَالَ وَيْحَكَ لَا تَفْتَحْهُ فَإِنَّكَ إِنْ فَتَحْتَهُ تَلِجْهُ فَالصِّرَاطُ الإِسْلَامُ وَالسُّورَانِ حُدُودُ اللهِ وَالْأَبْوَابُ الْمُفَتَّحَةُ مَحَارِمُ اللهِ وَذَلِكَ الدَّاعِي عَلَى رَأْسِ الصِّرَاطِ كِتَابُ اللهِ، وَالدَّاعِي مِنْ فَوْقِ الصِّرَاطِ وَاعِظُ اللهِ فِي قَلْبِ كُلِّ مُسْلِم»

(Allah has given a parable of the straight path, and on the two sides of this path, there are two walls containing door ways. On these door ways, there are curtains that are lowered down. on the gate of this path there is a caller heralding, `O people! come and enter the straight path all together and do not divide. ' There is also another caller that heralds from above the path, who says when a person wants to remove the curtain on any of these doors, `Woe to you! Do not open this door, for if you open it, you will enter it. The (straight) path is Islam, the two walls are Allah's set limits, the open doors lead to Allah's prohibitions, the caller on the gate of the path is Allah's Book (the Qur'an), while the caller from above the path is Allah's admonition in the heart of every Muslim.) At-Tirmidhi and An-Nasa'i also recorded this Hadith, and At-Tirmidhi said, "Hasan Gharib." Allah's statement,

فَاتَّبِعُوهُ وَلاَ تَتَّبِعُواْ السُّبُلَ

(so follow it, and follow not (other) paths...) describes Allah's path in the singular sense, because truth is one. Allah describes the other paths in the plural, because they are many and are divided. Allah said in another Ayah,

اللَّهُ وَلِيُّ الَّذِينَ ءامَنُواْ يُخْرِجُهُم مِّنَ الظُّلُمَـتِ إِلَى النُّورِ وَالَّذِينَ كَفَرُواْ أَوْلِيَآؤُهُمُ الطَّـغُوتُ يُخْرِجُونَهُم مِّنَ النُّورِ إِلَى الظُّلُمَـتِ أُوْلَـئِكَ أَصْحَـبُ النَّارِ هُمْ فِيهَا خَـلِدُونَ

(Allah is the Wali (Protector or Guardian) of those who believe. He brings them out from darknesses into light. But as for those who disbelieve, their supporters are Taghut (false deities), they bring them out from light into darknesses. Those are the dwellers of the Fire, and they will abide therein forever.) 2:257

Tafsir Ibn Kathir (abridged, English).