Sahih Muslim
The Book of Knowledge (Kitab Al-Ilm)
Book Number: 034 / Hadith Number: 6470
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: He who called (people) to righteousness, there would be reward (assured) for him like the rewards of those who adhered to it, without their rewards being diminished in any respect. And he who called (people) to error, he shall have to carry (the burden) of its sin, like those who committed it, without their sins being diminished in any respect.