Is it obligatory for a full-time preacher, who engages in da‘wah through lectures and modern means, to advise every individual he sees committing a specific wrong, or is what he offers by way of general da‘wah sufficient? And would he be sinful if he does not advise the one committing the wrong that he witnesses?

Enjoining good and forbidding evil is a sign that one desires good for its doer, and it is a communal obligation (fard kifaya). Its importance increases with the spread of evils. The one who is able must forbid evil with his hand or his tongue, and if he is unable, then with his heart, which is the weakest of faith. Efforts in calling to good do not suffice for forbidding evil if the conditions for its obligation are met.