Tafsir of At-Tawbah 9:13

{Will you not fight a people...} The interrogative particle (hamza) is prefixed to {you do not fight} to confirm the absence of fighting. Its meaning is to incite them to fight in a hyperbolic manner.

{Who broke their oaths} Which they swore in the treaty.

{And determined to expel the Messenger} From Mecca, when they consulted about his affair in the Dar al-Nadwa, until Allah, the Exalted, permitted him to migrate, so he departed himself.

{And they began [the aggression against] you the first time} Meaning: They are the ones who initiated the fighting. This is because the Messenger of Allah (peace be upon him) first brought them the illuminating Book and challenged them with it. Being unable to match it, they turned away from opposition to fighting; thus, they are the initiators of the combat, and the initiator is more unjust. What, then, prevents you from fighting them in kind, and confronting them with evil just as they confronted you?

He rebukes them for abandoning the fight against them and incites them to it, then describes the enemies with traits that necessitate such incitement. He establishes that whoever possesses such qualities—breaking covenants, expelling the Messenger, and initiating combat without cause—deserves to be confronted, and whoever neglects this deserves to be rebuked.

{Do you fear them?} A confirmation of their fear of them and a rebuke for it.

{But Allah has more right that you should fear Him} So you should fight His enemies.

{If you are believers} Meaning that the requirement of true faith is that a believer fears none but his Lord and pays no heed to anyone else, as in His saying: {And they fear none but Allah} (Al-Ahzab: 39).

{Fight them; Allah will punish them by your hands and will disgrace them and give you victory over them and heal the breasts of a believing people. And remove the fury in their hearts. And Allah turns in forgiveness to whom He wills; and Allah is Knowing, Wise.}