﴿ لَوْ كَانَ عَرَضًۭا قَرِيبًۭا وَسَفَرًۭا قَاصِدًۭا لَّٱتَّبَعُوكَ وَلَٰكِنۢ بَعُدَتْ عَلَيْهِمُ ٱلشُّقَّةُ ۚ وَسَيَحْلِفُونَ بِٱللَّهِ لَوِ ٱسْتَطَعْنَا لَخَرَجْنَا مَعَكُمْ يُهْلِكُونَ أَنفُسَهُمْ وَٱللَّهُ يَعْلَمُ إِنَّهُمْ لَكَٰذِبُونَ ﴾

“Had there been [a prospect of] immediate gain, and an easy journey, they would certainly have followed thee, [O Prophet:] but the distance was too great for them. And yet, [after your return, O believers,] they will swear by God, "Had we been able to do so, we would certainly have set out with you!" - [and by thus falsely swearing] they will be destroying their own selves: for God knows indeed that they are lying!”

The fifth verse (42) mentions an excuse offered by those who did not participate in the Jihad because of negligence and lethargy. It was rejected as unacceptable because they did not use the ability given by Allah to pick and choose the right thing to do in His way. Therefore, the excuse of not having that ability is not valid.