Jareer bin Abdullah reported,

The Messenger of Allah ﷺ said, "Whoever introduces a good practice in Islam that is followed after him will be credited with a reward equal to that of everyone who acts upon it, without diminishing their rewards in any way. And whoever introduces an evil practice in Islam that is followed after him will bear a burden equal to that of everyone who acts upon it, without diminishing their burdens in any way."In another narration, the narrator said, I was sitting with the Messenger of Allah ﷺ in the early part of the day when a group of people came to him, barefoot and nearly naked, wrapped in striped woolen cloaks, or just cloaks, with swords slung over their shoulders. Most of them, indeed all of them, were from Mudar. The face of the Messenger of Allah ﷺ changed when he saw the poverty they were in. He went inside, then came out and ordered Bilal to give the call to prayer and the iqamah. He led the prayer, then delivered a sermon, saying, "People, fear your Lord, who created you from a single soul and created from it its mate and dispersed from both of them..." until the end of the verse, "...indeed, Allah is ever, over you, an Observer" [Nisa 4:1], and the verse in al-Hashr, "You who believe, fear Allah, and let every soul look to what it has put forth for tomorrow, and fear Allah" [Hashr 59:18].Then he said, "Let a man give in charity from his Dinar, from his dirham, from his garment, from a sa of his wheat, from a sa of his dates," until he said, "even if it be half a date."A man from the Ansar then came with a pouch so heavy his hand could barely lift it, in fact, it could not. Then the people followed in succession, until I saw two heaps, one of food and one of clothing. I saw the face of the Messenger of Allah ﷺ glowing as if it were gilded with gold.The Messenger of Allah ﷺ said, "Whoever introduces a good practice in Islam will have its reward and the reward of all who act upon it after him, without their rewards being diminished in any way. And whoever introduces an evil practice in Islam will bear its burden and the burden of all who act upon it after him, without their burdens being diminished in any way."

عن جرير بن عبد الله، قال

قال رسول الله ﷺ: من سن في الإسلام سنة حسنة، فعمل بها بعده، كتب له مثل أجر من عمل بها، ولا ينقص من أجورهم شيء. ومن سن في الإسلام سنة سيئة فعمل بها بعده، كتب عليه مثل وزر من عمل بها، ولا ينقص من أوزارهم شيء. وفي رواية: قال: كنت جالسا عند رسول الله ﷺ في صدر النهار، قال: فجاءه قوم حفاة عراة مجتابي النمار- أو العباء- متقلدي السيوف، عامتهم من مضر بل كلهم من مضر، فتمعر وجه رسول الله ﷺ لما رأى بهم من الفاقة، فدخل، ثم خرج، فأمر بلالا فأذن وأقام، فصلى ثم خطب فقال: {يأيها الناس اتقوا ربكم الذى خلقكم من نفس واحدة وخلق منها زوجها وبث منهما} إلى آخر الآية: {إن الله كان عليكم رقيبا} [سورة النساء: ١]، والآية التي في الحشر: {يأيها الذين ءامنوا اتقوا الله ولتنظر نفس ما قدمت لغد واتقوا الله} [الحشر: ١٨]. تصدق رجل من ديناره، من درهمه، من ثوبه، من صاع بره، من صاع تمره، حتى قال: ولو بشق تمرة. قال: فجاء رجل من الأنصار بصرة كادت كفه تعجز عنها، بل قد عجزت. قال: ثم تتابع الناس حتى رأيت كومين من طعام وثياب حتى رأيت وجه رسول الله ﷺ يتهلل كأنه مذهبة، فقال رسول الله ﷺ: من سن في الإسلام سنة حسنة فله أجرها وأجر من عمل بها بعده من غير أن ينقص من أجورهم شيء، ومن سن في الإسلام سنة سيئة كان عليه وزرها ووزر من عمل بها من بعده من غير أن ينقص من أوزارهم شيء.