(Fight in the way of Allah against those who fight against you…) [2:190].
Said al-Kalbi> Abu Salih> Ibn 'Abbas: “These verses were revealed concerning the treaty of Hudaybiyyah. This is because when the Messenger of Allah, Allah bless him and give him peace, and his Companions were barred from entering the Sacred House, he immolated his sacrificial offering in Hudaybiyyah. He then signed a treaty with the idolaters which stipulated that he would go back to Medina and return the following year. Mecca will be vacated for him for three days during which he can circumambulate the Sacred House and do there whatever he wished. The Messenger of Allah, Allah bless him and give him peace, agreed to sign this treaty. In the following year, the Messenger of Allah, Allah bless him and give him peace, and his Companions got ready to perform the lesser pilgrimage which they had missed but, at the same time, were afraid that Quraysh would not honour their treaty, bar them from the Sacred House and fight them. The prophetic Companions were apprehensive of fighting them during the Sacred months and in the Sacred Precinct. And so Allah, exalted is He, revealed (Fight in the way of Allah against those who fight against you), i.e. the Quraysh”.
Asbab Al-Nuzul by Al-Wahidi , trans. Mokrane Guezzou