AbdurRahman ibn Amr as-Sulami and Hujr ibn Hujr said: We came to Irbad ibn Sariyah who was among those about whom the following verse was revealed: "Nor (is there blame) on those who come to thee to be provided with mounts, and when thou saidst: "I can find no mounts for you." We greeted him and said: We have come to see you to give healing and obtain benefit from you. Al-Irbad said: One day the Messenger of Allah ﷺ led us in prayer, then faced us and gave us a lengthy exhortation at which the eyes shed tears and the hearts were afraid. A man said: Messenger of Allah! It seems as if it were a farewell exhortation, so what injunction do you give us? He then said: I enjoin you to fear Allah, and to hear and obey even if it be an Abyssinian slave, for those of you who live after me will see great disagreement. You must then follow my sunnah and that of the rightly-guided caliphs. Hold to it and stick fast to it. Avoid novelties, for every novelty is an innovation, and every innovation is an error. (Using translation from Abū Dāʾūd 4607)  

الْعِرْبَاضُ صَلَّى بِنَا رَسُولُ اللَّهِ ﷺ الصُّبْحَ ذَاتَ يَوْمٍ ثُمَّ أَقْبَلْ عَلَيْنَا فَوَعَظَنَا مَوْعِظَةً بَلِيغَةً ذَرَفَتْ مِنْهَا الْعُيُونُ وَوَجِلَتْ مِنْهَا الْقُلُوبُ فَقَالَ قَائِلٌ يَا رَسُولَ اللَّهِ كَأَنَّهَا مَوْعِظَةُ مُوَدَّعٍ فَمَا تَعْهَدُ إِلَيْنَا؟ فَقَالَ «أُوصِيكُمْ بِتَقْوَى اللَّهِ وَالسَّمْعِ وَالطَّاعَةِ وَإِنْ كَانَ عَبْدًا حَبَشِيًّا فَإِنَّهُ مَنْ يَعِشْ مِنْكُمْ فَسَيَرَى اخْتِلَافًا كَثِيرًا فَعَلَيْكُمْ بِسُنَّتِي وَسُنَّةِ الْخُلَفَاءِ الرَّاشِدِينَ الْمَهْدِيِّينَ فَتَمَسَّكُوا بِهَا وَعَضُّوا عَلَيْهَا بِالنَّوَاجِذِ وَإِيَّاكُمْ وَمُحْدَثَاتِ الْأُمُورِ فَإِنَّ كُلَّ مُحْدَثَةٍ بِدْعَةٌ وَكُلَّ بِدْعَةٍ ضَلَالَةٌ»