משנה אויף דברים 4:32

They may not expound upon the subject of forbidden relations in the presence of three. Nor the work of creation in the presence of two. Nor [the work of] the chariot in the presence of one, unless he is a sage and understands of his own knowledge. Whoever speculates upon four things, it would have been better had he not come into the world: what is above, what is beneath, what came before, and what came after. And whoever takes no thought for the honor of his creator, it would have been better had he not come into the world.