Is the saying, "He who said, 'I do not know' or 'I am not sure' has issued a fatwa," a sound hadith? And if it is not a hadith, does its meaning conform to the teachings of Islam and the methodology of the Salaf?

The saying "I do not know is half of knowledge" is not a prophetic hadith (definition); rather, it is a statement from wise people and scholars. It means that the questioner knows that the one being asked does not possess the information, so they should ask someone else. This aligns with the methodology of Islam, which forbids speaking about the religion of Allah without knowledge, as stated in the Almighty's words: "And do not say about what your tongues falsely describe, 'This is lawful and this is unlawful,' to invent falsehood against Allah. Indeed, those who invent falsehood against Allah will not succeed" (Quran 16:116), and the Prophet, peace and blessings be upon him, said: "Whoever intentionally lies about me, let him take his seat in the Hellfire." Ali, may Allah be pleased with him, said: "And one who knows, when asked about what he does not know, should not be ashamed to say, 'Allah knows best.'" Malik said: "It is from the understanding of a scholar to say, 'I do not know.'" And Al-Sha'bi said: "I do not know is half of knowledge."