﴿ لَّيْسَ عَلَى ٱلضُّعَفَآءِ وَلَا عَلَى ٱلْمَرْضَىٰ وَلَا عَلَى ٱلَّذِينَ لَا يَجِدُونَ مَا يُنفِقُونَ حَرَجٌ إِذَا نَصَحُوا۟ لِلَّهِ وَرَسُولِهِۦ ۚ مَا عَلَى ٱلْمُحْسِنِينَ مِن سَبِيلٍۢ ۚ وَٱللَّهُ غَفُورٌۭ رَّحِيمٌۭ ﴾

“[But] no blame shall attach to the weak, nor to the sick, nor to those who have no means. [to equip themselves], provided that they are sincere towards God and His Apostle: there is no cause to reproach the doers of good, for God is much-forgiving, a dispenser of grace.”

As for the weak such as the old and the sick the blind and the chronically ill and those who find nothing to expend for the struggle no blame no sin falls upon them should they stay away from it if they remain true to God and to His Messenger when they stay behind by not spreading false rumours or impeding others from joining the struggle but by adhering to obedience. There is no way of blame no way of reproach against those who are virtuous through such behaviour. And God is Forgiving Merciful to them by granting them such leeway in this matter.