At-Taubah - 9:44

لاَ يَسْتَأْذِنُكَ الَّذِينَ يُؤْمِنُونَ بِاللّهِ وَالْيَوْمِ الآخِرِ أَن يُجَاهِدُواْ بِأَمْوَالِهِمْ وَأَنفُسِهِمْ وَاللّهُ عَلِيمٌ بِالْمُتَّقِينَ
[9:44]
They do not ask leave of you who believe in Allah and the latter day (to stay away) from striving hard with their property and their persons, and Allah knows those who guard (against evil).
Those who believe in Allah and the Last Day ask thee for no exemption from fighting with their goods and persons. And Allah knoweth well those who do their duty.
Those who believe in Allah and the Last Day ask no leave of thee lest they should strive with their wealth and their lives. Allah is Aware of those who keep their duty (unto Him).