Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(And if they) the people of Mecca (break their pledges) which are between you and them (after their treaty (has been made with you) and assail your religion) and defame the Religion of Islam, (then fight the heads of disbelief) fight the leaders of disbelief: Abu Sufyan and his host. (Lo! they have no binding oaths in order that they may desist) from breaking their pledges.
But if they break, [if] they violate, their oaths, their covenants, after [making] their pact and assail your religion, slander it, then fight the leaders of unbelief, its heads (here an overt noun [‘the leaders of unbelief’] has replaced the [third person] pronominalisation) — verily they have no [binding] oaths, [no] pacts (a variant reading [for aymān, ‘oaths’] has the kasra inflection [for the alif, sc. īmān, ‘[no] faith’]) — so that they might desist, from unbelief.
Allah says, if the idolators with whom you conducted peace treaties for an appointed term break
(their oaths) meaning, terms of their treaties, and covenants
وَطَعَنُواْ فِى دِينِكُمْ
(and attack your religion...) with disapproval and criticism, it is because of this that one who curses the Messenger, peace be upon him, or attacks the religion of Islam by way of criticism and disapproval, they are to be fought. This is why Allah said afterwards,
(then fight (you) against the leaders of disbelief -- for surely, their oaths are nothing to them -- so that they may stop.) so that they may refrain from the disbelief, rebellion and the transgression they indulge in. Qatadah and others said that the leaders of disbelief were Abu Jahl, `Utbah and Shaybah, Umayyah bin Khalaf, and he went on to mention several others. Al-A`mash narrated from Zayd bin Wahb from Hudhayfah; "The people of this Ayah were never fought again.'' A similar statement was reported from `Ali bin Abi Talib, may Allah be pleased with him. However, this Ayah is general, even though the specific reason behind revealing it was the idolators of Quraysh. So this Ayah generally applies to them and others as well, Allah knows best. Al-Walid bin Muslim said that Safwan bin `Amr narrated that `Abdur-Rahman bin Jubayr bin Nufayr said that when Abu Bakr sent an army to Ash-Sham, he advised them, "You will find some people with shaved heads. Therefore, strike the swords upon the parts that contain the devil, for by Allah, it is better to me to kill one of these people than to kill seventy other men. This is because Allah said,
فَقَـتِلُواْ أَئِمَّةَ الْكُفْرِ
(then fight (you) against the leaders of disbelief.)'' Ibn Abi Hatim collected it.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
That is, "When they had to make a choice between the Divine Guidance and the transitory worldly ambitions, they chose the latter, because they did not comprehend the comparative values of the two. Whereas the Revelations of Allah were inviting them to goodness, righteousness and observance of the Divine Law, which lead to eternal bliss, they chose to follow the unbridled lusts of their selves which gained some transitory worldly benefits for them, but consequently led them to eternal perdition.
Those evil-doers "blocked His Way for others", for they not only chose misguidance for themselves but also tried to prevent others from following the right way. They put every kind of obstruction in the way of the invitation to righteousness; nay, they tried their worst to gag the mouths of those who were extending that invitation and make their lives hard for them. In short, they did all they could to prevent the establishment of the righteous system of life that Allah required the people to establish.
Here, too, it has explicitly been stated that those who repent will not become your brethren in faith without the observance of Salat and Zakat.
"Yet if........they shall be your brethren in faith": This means that "if they fulfill those conditions, then not only shall their lives and properties become unlawful for you but also they shall enjoy equal rights with you in the Islamic Community. There shall be no distinction between them and the other Muslims in regard to social, cultural, legal and political rights, and nothing will stand in their way to the progress for which they are otherwise qualified.
"........you should fight with them.....":perhaps the fear of war may force them to desist from breaking oaths and reviling Islam.
In the context,the words, oaths and compacts mean the compact of the acceptance of Islam. Therefore, the question of making a new compact with them does not arise. As regards the old pacts, they had already broken all of them. It is on account of this that the declaration of immunity (from obligations) by Allah and His Messenger has been clearly made. It has also been stated that such people are not worthy of any treaty and they can only be let off if they repent of their disbelief and shirk and establish Salat and pay Zakat dues. This verse states clearly how the renegades should be treated. As a matter of fact,.this verse forestalled the mischief of apostasy that broke out a year and a half after its revelation and Hadrat Abu Bakr followed the guidance given in this verse to crush it. (For further explanation, see my book entitled Murtad ki Saza Islami Qanun men).
(And if they break their pledges after their treaty (hath been made with you) and assail your religion, then fight the heads of disbelief…) [9:12]. Said Ibn 'Abbas: “This verse was revealed about Abu Sufyan ibn Harb, al-Harith ibn Hisham, Suhayl ibn 'Amr, 'Ikrimah ibn Abi Jahl and all the chiefs of Quraysh who broke their pledges, and these are the ones who planned to expel the Messenger of Allah”.