Sunan Ibn Majah Book 0, Hadith 209

حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا زَيْدُ بْنُ الْحُبَابِ، حَدَّثَنَا كَثِيرُ بْنُ عَبْدِ اللَّهِ بْنِ عَمْرِو بْنِ عَوْفٍ الْمُزَنِيُّ، حَدَّثَنِي أَبِي، عَنْ جَدِّي، أَنَّ رَسُولَ اللَّهِ ـ صلى الله عليه وسلم ـ قَالَ ‏ "‏ مَنْ أَحْيَا سُنَّةً مِنْ سُنَّتِي فَعَمِلَ بِهَا النَّاسُ كَانَ لَهُ مِثْلُ أَجْرِ مَنْ عَمِلَ بِهَا لاَ يَنْقُصُ مِنْ أُجُورِهِمْ شَيْئًا وَمَنِ ابْتَدَعَ بِدْعَةً فَعُمِلَ بِهَا كَانَ عَلَيْهِ أَوْزَارُ مَنْ عَمِلَ بِهَا لاَ يَنْقُصُ مِنْ أَوْزَارِ مَنْ عَمِلَ بِهَا شَيْئًا ‏"‏ ‏.‏

Kathir bin 'Abdullah bin 'Amr bin 'Awf Al-Muzani said:"My father told me narrating from my grandfather, that the Messenger of Allah said: 'Whoever revives a Sunnah of mine, which people then act upon, will have a reward equivalent to that of those who act upon it, without that detracting from their reward in the slightest. And whoever introduces an innovation (Bid'ah) that is acted upon, will have a burden of sins equivalent to that of those who act upon it, withot that detracting from the burden of those who act upon it in the slightest