Word by Word Analysis

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 81

Those who remained behind rejoiced in their staying [at home] after [the departure of] the Messenger of Allāh and disliked to strive with their wealth and their lives in the cause of Allāh and said, "Do not go forth in the heat." Say, "The fire of Hell is more intense in heat" - if they would but understand.