Prevent occurrences of evil and the least one can do is reject it in their heart

It was Marwan who initiated (the practice) of delivering khutbah (address) before the prayer on the 'Id day. A man stood up and said: Prayer should precede khutbah. He (Marwan) remarked, This (practice) has been done away with. Upon this Abu Sa'id remarked: This man has performed (his duty) laid on him. I heard the Messenger of Allah as saying: He who amongst you sees something abominable should modify it with the help of his hand; and if he has not strength enough to do it, then he should do it with his tongue, and if he has not strength enough to do it, (even) then he should (abhor it) from his heart, and that is the least of faith.  

أَوَّلُ مَنْ بَدَأَ بِالْخُطْبَةِ يَوْمَ الْعِيدِ قَبْلَ الصَّلاَةِ مَرْوَانُ، فَقَامَ إِلَيْهِ رَجُلٌ فَقَالَ: الصَّلاَةُ قَبْلَ الْخُطْبَةِ۔ فَقَالَ قَدْ تُرِكَ مَا هُنَالِكَ۔ فَقَالَ أَبُو سَعِيدٍ: أَمَّا هَذَا فَقَدْ قَضَى مَا عَلَيْهِ سَمِعْتُ رَسُولَ اللَّهِ ﷺ يَقُولُ: «مَنْ رَأَى مِنْكُمْ مُنْكَرًا فَلْيُغَيِّرْهُ بِيَدِهِ، فَإِنْ لَمْ يَسْتَطِعْ فَبِلِسَانِهِ، فَإِنْ لَمْ يَسْتَطِعْ فَبِقَلْبِهِ وَذَلِكَ أَضْعَفُ الإِيمَانِ۔»  

The same hadith of the Prophet (may peace and blessings be upon him) has been reported by Abu Sa'id al-Khudri in connection with the story of Marwan.  

عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ فِي قِصَّةِ مَرْوَانَ وَحَدِيثِ أَبِي سَعِيدٍ عَنِ النَّبِيِّ ﷺ بِمِثْلِ حَدِيثِ شُعْبَةَ وَسُفْيَانَ  

Never a Prophet had been sent before me by Allah towards his nation who had not among his people (his) disciples and companions who followed his ways and obeyed his command. Then there came after them their successors who said whatever they did not practise, and practised whatever they were not commanded to do. He who strove against them with his hand was a believer: he who strove against them with his tongue was a believer, and he who strove against them with his heart was a believer and beyond that there is no faith even to the extent of a mustard seed. Abu Rafi' said: I narrated this hadith to 'Abdullah b. 'Umar; he contradicted me. There happened to come 'Abdullah b. Mas'ud who stayed at Qanat, and 'Abdullah b 'Umar wanted me to accompany him for visiting him (as 'Abdullah b. Mas'ud was ailing), so I went along with him and as we sat (before him) I asked Ibn Mas'ud about this hadith. He narrated it in the same way as I narrated it to Ibn 'Umar.  

أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ مَا مِنْ نَبِيٍّ بَعَثَهُ اللَّهُ فِي أُمَّةٍ قَبْلِي إِلاَّ كَانَ لَهُ مِنْ أُمَّتِهِ حَوَارِيُّونَ وَأَصْحَابٌ يَأْخُذُونَ بِسُنَّتِهِ وَيَقْتَدُونَ بِأَمْرِهِ ثُمَّ إِنَّهَا تَخْلُفُ مِنْ بَعْدِهِمْ خُلُوفٌ يَقُولُونَ مَا لاَ يَفْعَلُونَ وَيَفْعَلُونَ مَا لاَ يُؤْمَرُونَ فَمَنْ جَاهَدَهُمْ بِيَدِهِ فَهُوَ مُؤْمِنٌ وَمَنْ جَاهَدَهُمْ بِلِسَانِهِ فَهُوَ مُؤْمِنٌ وَمَنْ جَاهَدَهُمْ بِقَلْبِهِ فَهُوَ مُؤْمِنٌ وَلَيْسَ وَرَاءَ ذَلِكَ مِنَ الإِيمَانِ حَبَّةُ خَرْدَلٍ قَالَ أَبُو رَافِعٍ فَحَدَّثْتُهُ عَبْدَ اللَّهِ بْنَ عُمَرَ فَأَنْكَرَهُ عَلَىَّ فَقَدِمَ ابْنُ مَسْعُودٍ فَنَزَلَ بِقَنَاةَ فَاسْتَتْبَعَنِي إِلَيْهِ عَبْدُ اللَّهِ بْنُ عُمَرَ يَعُودُهُ فَانْطَلَقْتُ مَعَهُ فَلَمَّا جَلَسْنَا سَأَلْتُ ابْنَ مَسْعُودٍ عَنْ هَذَا الْحَدِيثِ فَحَدَّثَنِيهِ كَمَا حَدَّثْتُهُ ابْنَ عُمَرَ قَالَ صَالِحٌ وَقَدْ تُحُدِّثَ بِنَحْوِ ذَلِكَ عَنْ أَبِي رَافِعٍ  

Never was there one among the prophets who had had not disciples who followed his direction and followed his ways. The remaining part of the hadith is like that as narrated by Salih but the arrival of Ibn Mas'ud and the meeting of Ibn 'Umar with him is not mentioned.  

عَنْ أَبِي رَافِعٍ مَوْلَى النَّبِيِّ ﷺ عَنْ عَبْدِ اللَّهِ بْنِ مَسْعُودٍ أَنَّ رَسُولَ اللَّهِ ﷺ قَالَ مَا كَانَ مِنْ نَبِيٍّ إِلاَّ وَقَدْ كَانَ لَهُ حَوَارِيُّونَ يَهْتَدُونَ بِهَدْيِهِ وَيَسْتَنُّونَ بِسُنَّتِهِ مِثْلَ حَدِيثِ صَالِحٍ وَلَمْ يَذْكُرْ قُدُومَ ابْنِ مَسْعُودٍ وَاجْتِمَاعَ ابْنِ عُمَرَ مَعَهُ