Sahih Muslim , Book 34, Hadith 6466 (USC-MSA) ⓘ

Jarir b. Abdullah reported that some desert Arabs clad in woollen clothes came to Allah's Messenger. He saw them in sad plight as they had been hard pressed by need. He (the Holy Prophet) exhorted people to give charity, but they showed some reluctance until (signs) of anger could be seen on his face. Then a person from the Ansar came with a purse containing silver. Then came another person and then other persons followed them in succession until signs of happiness could be seen on his (sacred) face. Thereupon Allah's Messenger said: He who introduced some good practice in Islam which was followed after him (by people) he would be assured of reward like one who followed it, without their rewards being diminished in any respect. And he who introduced some evil practice in Islam which had been followed subsequently (by others), he would be required to bear the burden like that of one who followed this (evil practice) without their's being diminished in any respect.

حَدَّثَنِي زُهَيْرُ بْنُ حَرْبٍ، حَدَّثَنَا جَرِيرُ بْنُ عَبْدِ الْحَمِيدِ، عَنِ الأَعْمَشِ، عَنْ مُوسَى، بْنِ عَبْدِ اللَّهِ بْنِ يَزِيدَ وَأَبِي الضُّحَى عَنْ عَبْدِ الرَّحْمَنِ بْنِ هِلاَلٍ الْعَبْسِيِّ، عَنْ جَرِيرِ بْنِ عَبْدِ، اللَّهِ قَالَ جَاءَ نَاسٌ مِنَ الأَعْرَابِ إِلَى رَسُولِ اللَّهِ صلى الله عليه وسلم عَلَيْهِمُ الصُّوفُ فَرَأَى سُوءَ حَالِهِمْ قَدْ أَصَابَتْهُمْ حَاجَةٌ فَحَثَّ النَّاسَ عَلَى الصَّدَقَةِ فَأَبْطَئُوا عَنْهُ حَتَّى رُئِيَ ذَلِكَ فِي وَجْهِهِ - قَالَ - ثُمَّ إِنَّ رَجُلاً مِنَ الأَنْصَارِ جَاءَ بِصُرَّةٍ مِنْ وَرِقٍ ثُمَّ جَاءَ آخَرُ ثُمَّ تَتَابَعُوا حَتَّى عُرِفَ السُّرُورُ فِي وَجْهِهِ فَقَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ مَنْ سَنَّ فِي الإِسْلاَمِ سُنَّةً حَسَنَةً فَعُمِلَ بِهَا بَعْدَهُ كُتِبَ لَهُ مِثْلُ أَجْرِ مَنْ عَمِلَ بِهَا وَلاَ يَنْقُصُ مِنْ أُجُورِهِمْ شَىْءٌ وَمَنْ سَنَّ فِي الإِسْلاَمِ سُنَّةً سَيِّئَةً فَعُمِلَ بِهَا بَعْدَهُ كُتِبَ عَلَيْهِ مِثْلُ وِزْرِ مَنْ عَمِلَ بِهَا وَلاَ يَنْقُصُ مِنْ أَوْزَارِهِمْ شَىْءٌ ‏" ‏ ‏.‏