What was the occasion of revelation of the fifth verse of Surat At-Tawbah?

Interpretation of the first verses of Surat At-Tawbah (definition), known as "Ayat Al-Bara'ah" (Verses of Disavowal), which give the polytheists who had no treaty, or whose treaty had expired, a grace period of four months to move about safely in the land. After this period, fighting them becomes permissible. As for those who had a fixed treaty and did not violate it or support anyone against the Muslims, their treaty must be fulfilled until its term.

The fifth verse of Surat At-Tawbah, which commands fighting the polytheists after the Sacred Months have passed if they do not repent, establish prayer, and pay zakat (definition), is known as "Ayat Al-Sayf" (the Sword Verse). The majority of scholars believe that it abrogates all verses that call for forgiveness and pardon of polytheists, and commands fighting them. However, others believe that "Ayat Al-Sayf" does not abrogate those verses, but rather that circumstances differ. If Muslims are strong, they act upon the Sword Verse and fight all disbelievers. If they are weak, there is no harm in refraining from fighting those who refrain from fighting them, and the matter is determined by expediency and considering the consequences. This latter view is the most preponderant.