Hadith: No prophet had been sent before me by Allah except that he had disciples and companions from his nation who adhered to his way and followed his command

عَنْ عَبْدِ اللهِ بْنِ مَسْعُودٍ رضي الله عنه أَنَّ رَسُولَ اللهِ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ قَالَ:
«مَا مِنْ نَبِيٍّ بَعَثَهُ اللهُ فِي أُمَّةٍ قَبْلِي إِلَّا كَانَ لَهُ مِنْ أُمَّتِهِ حَوَارِيُّونَ، وَأَصْحَابٌ يَأْخُذُونَ بِسُنَّتِهِ وَيَقْتَدُونَ بِأَمْرِهِ، ثُمَّ إِنَّهَا تَخْلُفُ مِنْ بَعْدِهِمْ خُلُوفٌ يَقُولُونَ مَا لَا يَفْعَلُونَ، وَيَفْعَلُونَ مَا لَا يُؤْمَرُونَ، فَمَنْ جَاهَدَهُمْ بِيَدِهِ فَهُوَ مُؤْمِنٌ، وَمَنْ جَاهَدَهُمْ بِلِسَانِهِ فَهُوَ مُؤْمِنٌ، وَمَنْ جَاهَدَهُمْ بِقَلْبِهِ فَهُوَ مُؤْمِنٌ، وَلَيْسَ وَرَاءَ ذَلِكَ مِنَ الْإِيمَانِ حَبَّةُ خَرْدَلٍ».
[صحيح] - [رواه مسلم] - [صحيح مسلم: 50]

‘Abdullah ibn Mas‘ūd (may Allah be pleased with him) reported that the Messenger of Allah (may Allah's peace and blessings be upon him) said:
"No prophet had been sent before me by Allah except that he had disciples and companions from his nation who adhered to his way and followed his command. They were, then, succeeded by successors who would say what they did not do and do what they were not commanded to do. Whoever strives against them with his hand is a believer; whoever strives against them with his tongue is a believer; whoever strives against them with his heart is a believer; and beyond that, there is no mustard seed's weight of faith."
[Authentic hadith] - [Narrated by Muslim] - [Sahih Muslim - 50]

Explanation

The Prophet (may Allah's peace and blessings be upon him) informed that no prophet had been sent by Allah to a nation before him except that he had close friends, supporters, and sincere fighters from among his nation who were qualified to succeed him, adopting his way and following his command. These righteous predecessors would, then, be succeeded by people who were void of goodness; claiming what they did not practice and practicing what they were not commanded to do. Whoever strives against them with his hand is a believer, whoever strives against them with his tongue is a believer, and whoever strives against them with his heart is a believer, but beyond that, there is no mustard seed's weight of faith.