Often people will cite Brahma Sahampati’s invitation after the Great Awakening as evidence that an invitation is required, along with Ananda’s failure to extend an invitation re the Buddha’s lifespan. But these are more mythic than direct and their meaning is debatable.
Also debatable are the cases where a monk didn’t teach what wasn’t asked for and then later the Buddha said something about it (e.g. Sariputta and the dying Brahmin, or the silent Uposatta monks). Are these examples of how we should be restrained? Or is the Buddha’s gentle admonishment proof that teachings should have happened there? The stories are, in my opinion, intentionally ambiguous.
One thing I have noticed is that while the Buddha is quick to reprimand the monastics, he’s usually quite hesitant to reprimand a lay person, usually requiring a triple invitation before giving negative feedback.
The Buddha himself compared his approach to a farmer: of course a farmer spends most of his time tending to the fertile field and only spends a little time planting seeds in the dry field. So too the Buddha spends most of his time teaching those who are eager to learn, and spends only little time on those who are not. [citation needed… can’t find the sutta now 
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In DN 12 this is called blameworthy:
It’s just as if a man, neglecting his own field, were to imagine that another’s field should be weeded. I say that such a thing is an evil, greedy deed, for what can one person do for another? This is a teacher who is worthy of criticism