Buddha says

Imagine a man who has been pierced by an arrow well soaked in poison, and his friends and relatives go at once to fetch a physician or a surgeon. Imagine now that this man says:
“I will not have this arrow pulled out until I know the name of the man who shot it, and the name of his family, and whether he is tall or short or of medium height; until I know whether he is black or dark or yellow; until I know his village or town. I will not have this arrow pulled out until I know about the bow that shot it, whether it was a long bow or a cross bow.
“I will not have this arrow pulled out until I know about the bow-string, and the arrow, and the feathers on the arrow, whether they are feathers of vulture, kite or peacock.
“I will not have this arrow pulled out until I know whether the tendon which binds it is of an ox, deer, or monkey.
“I will not have this arrow pulled out until I know whether it is an arrow, or the edge of a knife, or a splinter, of the tooth of a calf, or the head of a javelin.”
Well that man would die, but he would die without having found out any of these things. In the same way, anyone who says: “I will not follow the holy life of Buddha until he tells me whether the world is eternal or not; whether the life and the body are two things, or one thing; whether the one who has reached the Goal is beyond death or not; whether he is both beyond death and not beyond death; whether he is neither beyond death nor is not beyond death.”
Well that man would die, but he would die without Buddha having told these things.
Because I am one who says: whether the world is eternal or not, there is birth, and death, and suffering, and woe, and lamentation, and despair. And what I do teach is the means that lead to the destruction of these things.
Remember therefore that what I have said, I have said; and what I have not said, I have not said. And why have I not given and answer to these things? Because these questions are not profitable, they are not a principle of the holy life, they lead not peace, to supreme wisdom, to Nirvana.

Majjhima Nikaya 1. 63