Quran 9:92 — Ultimatum (Bara'ah)

Also excused are those who come to you wishing to be included with you, but you tell them, "I do not have anything to carry you on." They then turn back with tears in their eyes, genuinely saddened that they could not afford to contribute.

[9:91] Not to be blamed are those who are weak, or ill, or do not find anything to offer, so long as they remain devoted to GOD and His messenger. The righteous among them shall not be blamed. GOD is Forgiver, Most Merciful.

[9:93] The blame is on those who ask your permission to stay behind, even though they have no excuse. They have chosen to be with the sedentary. Consequently, GOD has sealed their hearts, and thus, they do not attain any knowledge.