To what extent may a Muslim interfere in the affairs of his Muslim brother?

Every Muslim must offer sincere advice to his Muslim brother concerning matters of his religion and his worldly affairs, for in the hadith: "Religion is sincere advice." So, a Muslim should advise his brother with wisdom if he sees him about to undertake something that will harm him. If he accepts the advice, that is what is desired. If he does not accept it, then he (the advisor) has absolved himself of responsibility. And among the rights of a Muslim upon a Muslim is to enjoin good and forbid evil, according to his ability, as the Prophet, peace and blessings be upon him, said: "Whoever among you sees an evil, let him change it with his hand; if he cannot, then with his tongue; if he cannot, then with his heart—and that is the weakest of faith."