Quran 9:44 — Ultimatum (Bara'ah)

Those who truly believe in GOD and the Last Day do not ask your permission to evade the opportunity to strive with their money and their lives. GOD is fully aware of the righteous.

[9:43] GOD has pardoned you: why did you give them permission (to stay behind), before you could distinguish those who are truthful from the liars?

[9:45] The only people who wish to be excused are those who do not really believe in GOD and the Last Day. Their hearts are full of doubt, and their doubts cause them to waver.