And if you do not, then be informed of a war [against (2:279)

Almuntakhab Fi Tafsir Alquran Alkarim

And if you do not obey this rule of righteous life commanded by religion, nor fearing for your unlawful gain, then you must expect war between belief against unbelief waged against you by Allah and His Prophet. But if you repent, grow wiser and reform then you are entitled only to the principal, the capital sum lent, so that you do not wrong others or be wronged

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(2:279) but if you do not do so, then you are warned of the declaration of war against you by Allah and His Messenger. *323 If, however, you repent even now (and forego interest), you are entitled to your principal; do no wrong, and no wrong will be done to you.

And if you do not, then be informed of a war [against meaning

*323). This verse was revealed after the conquest of Makka and has been placed here because of its contextual relevance. Although interest was considered objectionable earlier, it had not been legally prohibited. After the revelation of this verse interest-bearing transactions became a punishable offence within the realm of Islam. The Prophet (peace he on him) warned the Arab tribes through his officials that war would be declared against them if they did not give up interest-bearing transactions. It was specified, for instance, in the agreement under which the Christians of Najran were granted internal autonomy under the suzerainty of the Islamic state, that if they continued to use interest, the agreement with them would be considered void and their action an act of belligerency. On the basis of the last words of the verse, Ibn 'Abbas, Hasan al-Baari, Ibn Sirin and Rabi' ibn Anas are of the view that anyone who takes interest within the boundaries of the Islamic State (Dar al-Islam) should be pressed to repudiate the transaction and recant and, if he persists, should be put to death. Others consider it sufficient to imprison such people and keep them in prison until they pledge to give up taking interest. (See Jassas's commentary, on verse 2: 278; see especially vol. 1, pp. 471 f. - Ed.)
 

And if you do not, then be informed of a war [against meaning in Urdu

لیکن اگر تم نے ایسا نہ کیا، تو آگاہ ہو جاؤ کہ اللہ اور اسکے رسول کی طرف سے تمہارے خلاف اعلان جنگ ہے اب بھی توبہ کر لو (اور سود چھوڑ دو) تو اپنا اصل سرمایہ لینے کے تم حق دار ہو نہ تم ظلم کرو، نہ تم پر ظلم کیا جائے