Musnad Abu Ya'la al-Mawsili 160:94

And with his chain of narration, that the Messenger of Allah, may Allah bless him and grant him peace, said: "Whoever calls to guidance, there shall be for him of the reward like the rewards of those who follow him, without their rewards being diminished in the slightest. And whoever calls to misguidance, there shall be upon him of the sin like the sins of those who follow him, without that diminishing their sins in the slightest."