Ramakrishna said this quote

What Brahman is cannot be described. All things in the world — the Vedas, the Puranas, the Tantras, the six systems of philosophy — have been defiled, like food that has been touched by the tongue, for they have been read or uttered by the tongue. Only one thing has not been defiled in this way, and that is Brahman. No one has ever been able to say what Brahman is.

~ Ramakrishna

You speak of doing good to the world. Is the world such a small thing? And who are you, pray, to do good to the world? First realise God, see Him by means of spiritual discipline. If He imparts power you can do good to others; otherwise not.

~ Ramakrishna

God has made different religions to suit different aspirants, times, and countries. All doctrines are only so many paths; but a path is by no means God himself. Indeed, one can reach God if one follows any of the paths with whole-hearted devotion...One may eat a cake with icing either straight or sidewise. It will taste sweet either way.

~ Ramakrishna

Only two kinds of people can attain self-knowledge: those who are not encumbered at all with learning, that is to say, whose minds are not over-crowded with thoughts borrowed from others; and those who, after studying all the scriptures and sciences, have come to realise that they know nothing.

~ Ramakrishna