My Commentary (don't take my word for it!)
This sutta is a teaching on being practical minded and about dealing with the matter at hand. Life is too short to waste time on metaphysical speculation that does not bring us closer to the truth. This does not mean that beliefs other than our own are not valid. It does mean that other beliefs are not the focus here in this practice. The Buddha was teaching one thing - the end of suffering.
If he declares to me that 'The cosmos is eternal,' that 'The cosmos is not eternal,' that 'The cosmos is finite,' that 'The cosmos is infinite,' that 'The soul & the body are the same,' that 'The soul is one thing and the body another,' that 'After death a Tathagata exists,' that 'After death a Tathagata does not exist,' that 'After death a Tathagata both exists & does not exist,' or that 'After death a Tathagata neither exists nor does not exist,' then I will live the holy life under him. If he does not declare to me that 'The cosmos is eternal,'... or that 'After death a Tathagata neither exists nor does not exist,' then I will renounce the training and return to the lower life."
Then, when it was evening, Ven. Malunkyaputta arose from seclusion and went to the Blessed One. On arrival, having bowed down, he sat to one side. As he was sitting there he said to the Blessed One, "Lord, just now, as I was alone in seclusion, this train of thought arose in my awareness: 'These positions that are undeclared, set aside, discarded by the Blessed One... I don't approve, I don't accept that the Blessed One has not declared them to me. I'll go ask the Blessed One about this matter. If he declares to me that "The cosmos is eternal,"... or that "After death a Tathagata neither exists nor does not exist," then I will live the holy life under him. If he does not declare to me that "The cosmos is eternal,"... or that "After death a Tathagata neither exists nor does not exist," then I will renounce the training and return to the lower life.'
"Lord, if the Blessed One knows that 'The cosmos is eternal,' then may he declare to me that 'The cosmos is eternal.' If he knows that 'The cosmos is not eternal,' then may he declare to me that 'The cosmos is not eternal.' But if he doesn't know or see whether the cosmos is eternal or not eternal, then, in one who is unknowing & unseeing, the straightforward thing is to admit, 'I don't know. I don't see.'... If he doesn't know or see whether after death a Tathagata exists... does not exist... both exists & does not exist... neither exists nor does not exist,' then, in one who is unknowing & unseeing, the straightforward thing is to admit, 'I don't know. I don't see.'"
"Malunkyaputta, did I ever say to you, 'Come, Malunkyaputta, live the holy life under me, and I will declare to you that 'The cosmos is eternal,' or 'The cosmos is not eternal,' or 'The cosmos is finite,' or 'The cosmos is infinite,' or 'The soul & the body are the same,' or 'The soul is one thing and the body another,' or 'After death a Tathagata exists,' or 'After death a Tathagata does not exist,' or 'After death a Tathagata both exists & does not exist,' or 'After death a Tathagata neither exists nor does not exist'?"
"No, lord."
"And did you ever say to me, 'Lord, I will live the holy life under the Blessed One and [in return] he will declare to me that 'The cosmos is eternal,' or 'The cosmos is not eternal,' or 'The cosmos is finite,' or 'The cosmos is infinite,' or 'The soul & the body are the same,' or 'The soul is one thing and the body another,' or 'After death a Tathagata exists,' or 'After death a Tathagata does not exist,' or 'After death a Tathagata both exists & does not exist,' or 'After death a Tathagata neither exists nor does not exist'?"
"No, lord."
"Then that being the case, foolish man, who are you to be claiming grievances/making demands of anyone?
"Malunkyaputta, if anyone were to say, 'I won't live the holy life under the Blessed One as long as he does not declare to me that "The cosmos is eternal,"... or that "After death a Tathagata neither exists nor does not exist,"' the man would die and those things would still remain undeclared by the Tathagata.
"It's just as if a man were wounded with an arrow thickly smeared with poison. His friends & companions, kinsmen & relatives would provide him with a surgeon, and the man would say, 'I won't have this arrow removed until I know whether the man who wounded me was a noble warrior, a brahman, a merchant, or a worker.' He would say, 'I won't have this arrow removed until I know the given name & clan name of the man who wounded me... until I know whether he was tall, medium, or short... until I know whether he was dark, ruddy-brown, or golden-colored... until I know his home village, town, or city... until I know whether the bow with which I was wounded was a long bow or a crossbow... until I know whether the bowstring with which I was wounded was fiber, bamboo threads, sinew, hemp, or bark... until I know whether the shaft with which I was wounded was wild or cultivated... until I know whether the feathers of the shaft with which I was wounded were those of a vulture, a stork, a hawk, a peacock, or another bird... until I know whether the shaft with which I was wounded was bound with the sinew of an ox, a water buffalo, a langur, or a monkey.'
He would say, 'I won't have this arrow removed until I know whether the shaft with which I was wounded was that of a common arrow, a curved arrow, a barbed, a calf-toothed, or an oleander arrow.' The man would die and those things would still remain unknown to him.
"In the same way, if anyone were to say, 'I won't live the holy life under the Blessed One as long as he does not declare to me that 'The cosmos is eternal,'... or that 'After death a Tathagata neither exists nor does not exist,' the man would die and those things would still remain undeclared by the Tathagata.
"Malunkyaputta, it's not the case that when there is the view, 'The cosmos is eternal,' there is the living of the holy life. And it's not the case that when there is the view, 'The cosmos is not eternal,' there is the living of the holy life. When there is the view, 'The cosmos is eternal,' and when there is the view, 'The cosmos is not eternal,' there is still the birth, there is the aging, there is the death, there is the sorrow, lamentation, pain, despair, & distress whose destruction I make known right in the here & now.
"It's not the case that when there is the view, 'The cosmos is finite,' there is the living of the holy life. And it's not the case that when there is the view, 'The cosmos is infinite,' there is the living of the holy life. When there is the view, 'The cosmos is finite,' and when there is the view, 'The cosmos is infinite,' there is still the birth, there is the aging, there is the death, there is the sorrow, lamentation, pain, despair, & distress whose destruction I make known right in the here & now.
"It's not the case that when there is the view, 'The soul & the body are the same,' there is the living of the holy life. And it's not the case that when there is the view, 'The soul is one thing and the body another,' there is the living of the holy life. When there is the view, 'The soul & the body are the same,' and when there is the view, 'The soul is one thing and the body another,' there is still the birth, there is the aging, there is the death, there is the sorrow, lamentation, pain, despair, & distress whose destruction I make known right in the here & now.
"It's not the case that when there is the view, 'After death a Tathagata exists,' there is the living of the holy life. And it's not the case that when there is the view, 'After death a Tathagata does not exist,' there is the living of the holy life. And it's not the case that when there is the view, 'After death a Tathagata both exists & does not exist,' there is the living of the holy life. And it's not the case that when there is the view, 'After death a Tathagata neither exists nor does not exist' there is the living of the holy life. When there is the view, 'After death a Tathagata exists'... 'After death a Tathagata does not exist'... 'After death a Tathagata both exists & does not exist'... 'After death a Tathagata neither exists nor does not exist,' there is still the birth, there is the aging, there is the death, there is the sorrow, lamentation, pain, despair, & distress whose destruction I make known right in the here & now.
"So, Malunkyaputta, remember what is undeclared by me as undeclared, and what is declared by me as declared. And what is undeclared by me? 'The cosmos is eternal,' is undeclared by me. 'The cosmos is not eternal,' is undeclared by me. 'The cosmos is finite'... 'The cosmos is infinite'... 'The soul & the body are the same'... 'The soul is one thing and the body another'... 'After death a Tathagata exists'... 'After death a Tathagata does not exist'... 'After death a Tathagata both exists & does not exist'... 'After death a Tathagata neither exists nor does not exist,' is undeclared by me.
"And why are they undeclared by me? Because they are not connected with the goal, are not fundamental to the holy life. They do not lead to disenchantment, dispassion, cessation, calming, direct knowledge, self-awakening, Unbinding. That's why they are undeclared by me.
"And what is declared by me? 'This is stress,' is declared by me. 'This is the origination of stress,' is declared by me. 'This is the cessation of stress,' is declared by me. 'This is the path of practice leading to the cessation of stress,' is declared by me. And why are they declared by me? Because they are connected with the goal, are fundamental to the holy life. They lead to disenchantment, dispassion, cessation, calming, direct knowledge, self-awakening, Unbinding. That's why they are declared by me.
"So, Malunkyaputta, remember what is undeclared by me as undeclared, and what is declared by me as declared."
That is what the Blessed One said. Gratified, Ven. Malunkyaputta delighted in the Blessed One's Words.
