Qur'an 9:81

فَرِحَ ٱلْمُخَلَّفُونَ بِمَقْعَدِهِمْ خِلَـٰفَ رَسُولِ ٱللَّهِ وَكَرِهُوٓا۟ أَن يُجَـٰهِدُوا۟ بِأَمْوَٰلِهِمْ وَأَنفُسِهِمْ فِى سَبِيلِ ٱللَّهِ وَقَالُوا۟ لَا تَنفِرُوا۟ فِى ٱلْحَرِّ ۗ قُلْ نَارُ جَهَنَّمَ أَشَدُّ حَرًّا ۚ لَّوْ كَانُوا۟ يَفْقَهُونَ

Those who were left behind rejoiced at sitting still behind the messenger of Allah, and were averse to striving with their wealth and their lives in Allah's way. And they said: Go not forth in the heat! Say: The fire of hell is more intense of heat, if they but understood.