To what extent is the hadith "I am at war with those who fight you, and at peace with those who make peace with you" authentic, what is its explanation, and what is the ruling on those who rebelled against Ali ibn Abi Talib (may Allah be pleased with him) based on the authenticity of this hadith?

This Hadith: "I am at war with those who fight you, and at peace with those who are at peace with you," has a weak chain of narration and is not authentic. All its طرق (transmission paths) are flawed, containing either mendacious or unknown narrators.

Even if we assume its authenticity, its meaning is that the Prophet, peace be upon him, is at war with those who harbor hatred and enmity towards his household (Ahl al-Bayt), not with those who had political disagreements among themselves. It is impermissible to interpret this Hadith in relation to what transpired between the Companions on the Day of the Camel and at Siffin, because their fighting was based on ijtihad (independent reasoning) and ta'wil (interpretation), not on enmity and hatred.

Ali ibn Abi Talib explicitly stated that they were brothers and that Allah would reunite them, citing the verse: "And We will remove whatever is in their breasts of resentment, [so they will be] brothers, on thrones facing each other" (Quran 15:47).

Thus, the war mentioned in the Hadith—if authentic—refers to heartfelt and combative animosity, and God forbid that the Companions of the Messenger of Allah, peace be upon him, should be of this status.