Abu Dawud Book 32, Hadith Number 4322.
Narated By Abdullah ibn Mas’ud : The Apostle of Allah (PBUH) said: The first defect that permeated Banu Isra’il was that a man (of them) met another man and said: O so-and-so, fear Allah, and abandon what you are doing, for it is not lawful for you. He then met him the next day and that did not prevent him from eating with him, drinking with him and sitting with him. When they did so. Allah mingled their hearts with each other.
He then recited the verse: “curses were pronounced on those among the children of Isra’il who rejected Faith, by the tongue of David and of Jesus the son of Mary”…up to “wrongdoers”.
He then said: By no means, I swear by Allah, you must enjoin what is good and prohibit what is evil, prevent the wrongdoer, bend him into conformity with what is right, and restrict him to what is right.