How did the Prophet, peace and blessings be upon him, say: "Indeed, I do not know what will be done with me in this world," while he is infallible from shirk and knows that he will not die upon disbelief?

Prophets are infallible in conveying messages from Allah, and from grave sins, and from ignoble minor sins. They may err in minor sins that do not indicate ignobleness, but they are not upheld in those errors. As for His, the Almighty's, saying: (Say, "I am not an innovation among the messengers, and I do not know what will be done with me or with you. I only follow what is revealed to me, and I am not but a clear warner.") Al-Ahqaf/9, what is meant by it is what Allah will do with him and his people in this world, such as illness and health, glory and humiliation, victory and defeat, and similar things, not what pertains to the Hereafter; because the Prophet, peace and blessings be upon him, knows that he will be in Paradise. The verse clarifies that the Messenger is a servant of Allah who does not know the unseen, and it has no relation to matters of disbelief or sins.