Is advice restricted to being requested, or is it offered without a request?

Is obligatory advice restricted to being requested, or is it offered without a request?
The Prophet (peace and blessings be upon him) said: So if you know that your brother has done something and you want to give him advice, you should advise him. And if he seeks your advice, advise him; the matter is more emphatic. That is, he says, “What do you say about such and such?” Do not deceive him. Otherwise, you initiate the advice to him even if he did not seek your advice; it is a confirmed sunnah. You initiate the advice to him. If you see that he is falling into something that harms him, advise him. Or if a commodity is not suitable for him or is adulterated, advise him regarding the matter in which you see benefit for your brother. It may become obligatory; the circumstances differ.