At-Taubah - 9:91

لَّيْسَ عَلَى الضُّعَفَاء وَلاَ عَلَى الْمَرْضَى وَلاَ عَلَى الَّذِينَ لاَ يَجِدُونَ مَا يُنفِقُونَ حَرَجٌ إِذَا نَصَحُواْ لِلّهِ وَرَسُولِهِ مَا عَلَى الْمُحْسِنِينَ مِن سَبِيلٍ وَاللّهُ غَفُورٌ رَّحِيمٌ
[9:91]
It shall be no crime in the weak, nor in the sick, nor in those who do not find what they should spend (to stay behind), so long as they are sincere to Allah and His Messenger; there is no way (to blame) against the doers of good; and Allah is Forgiving, Merciful;
There is no blame on those who are infirm, or ill, or who find no resources to spend (on the cause), if they are sincere (in duty) to Allah and His Messenger: no ground (of complaint) can there be against such as do right: and Allah is Oft-forgiving, Most Merciful.
Not unto the weak nor unto the sick nor unto those who can find naught to spend is any fault (to be imputed though they stay at home) if they are true to Allah and His messenger. Not unto the good is there any road (of blame). Allah is Forgiving, Merciful.