Introduction to 1.3.3 Pāraṅgamasuttaṃ(The Going Beyond)
According to the scriptures it is a natural course of event, that Buddhas teach Dhamma only when requested. Two conditions have to be fulfilled, one internal cause: - ajjhatika nidāna -, the immense feeling of compassion of the Buddha for the world and the suffering in ignorance, and one external cause: -bāhira nidāna- the request of the highest being, mostly respected in the world: -lokagaru-.
“This is an inherent necessity (dhammatā) with all Tathāgatā, that they teach Dhamma only on request of a Brahma. And what is the reason for this? It is because at those times, all mankind including all mendicants, all Sāmaṇas and Brāhmiṇs, worship Brahma, revere Brahma and adore Brahma. Then if therefore such a powerful, glorious, well known, wise, high and mighty being pays his respect then the whole world including devas will feel inclined, trusts and take courage to pay respect in the same way, that is why, oh great king, a Tathāgatā proclaims the Dhamma only when requested by a Brahma.”