Tafsir of Al-Anfal 8:39

"And fight them until there is no fitnah..."

(And fight them) is a conjunction to "Say," and the address is generalized to further encourage the believers to engage in combat in order to realize what is implied by His, the Glorified, saying: "the precedent of the ancients has already passed" regarding the warning.

(Until there is no fitnah) meaning: until there is no shirk [polytheism] among them, as was narrated from Ibn Abbas and al-Hasan. It was also said: the intent is until no believer is tempted away from his religion.

(And the religion is all for Allah) and all false religions perish, either through the destruction of all their people or their abandonment of them out of fear of being killed. It has been said: The interpretation of this verse has not yet occurred, and its content will be realized when the Mahdi appears, for there will not remain a single polytheist on the face of the earth, according to what was narrated from Abu Abdullah, may Allah be pleased with him.

(So if they cease) from disbelief due to your fighting (then Allah is All-Seeing of what they do).

The sentence stands in the place of the [result of the] conditional clause; meaning: He will reward them for their ceasing and their conversion to Islam, or it is treated as a metaphor for the reward, or a metonymy. Otherwise, His, the Exalted, being All-Seeing is a fixed matter before and after their ceasing; it is not dependent on anything.

It is narrated from Ya’qub that he recited (what you do) with a ta [second person], as an address to the striving Muslims—meaning: [All-Seeing] of what you do of jihad, which brings them to Islam. The rewarding is linked to their ceasing to indicate that they [the Muslims] are rewarded for the causality, just as those who perform the action are rewarded for the performance itself.