Quran 2:190 — The Heifer (Al-Baqarah)

You may fight in the cause of GOD against those who attack you, but do not aggress. GOD does not love the aggressors.

[2:189] They ask you about the phases of the moon! Say, "They provide a timing device for the people, and determine the time of Hajj." It is not righteous to beat around the bush; righteousness is attained by upholding the commandments and by being straightforward. You shall observe GOD, that you may succeed.

[2:191] You may kill those who wage war against you, and you may evict them whence they evicted you. Oppression is worse than murder. Do not fight them at the Sacred Masjid, unless they attack you therein. If they attack you, you may kill them. This is the just retribution for those disbelievers.