Narrated Abu Sa`id Al-Khudri:

During the lifetime of Allah's Messenger (ﷺ) , some men among the hypocrites used to remain behind him (i.e. did not accompany him) when he went out for a Ghazwa and they would be pleased to stay at home behind Allah's Messenger (ﷺ) When Allah's Messenger (ﷺ) returned (from the battle) they would put forward (false) excuses and take oaths, wishing to be praised for what they had not done. So there was revealed:-- "Think not that those who rejoice in what they have done, and love to be praised for what they have not done.." (3:188)

حَدَّثَنَا سَعِيدُ بْنُ أَبِي مَرْيَمَ، أَخْبَرَنَا مُحَمَّدُ بْنُ جَعْفَرٍ، قَالَ حَدَّثَنِي زَيْدُ بْنُ أَسْلَمَ، عَنْ عَطَاءِ بْنِ يَسَارٍ، عَنْ أَبِي سَعِيدٍ الْخُدْرِيِّ ـ رضى الله عنه ـ أَنَّ رِجَالاً مِنَ الْمُنَافِقِينَ عَلَى عَهْدِ رَسُولِ اللَّهِ صلى الله عليه وسلم كَانَ إِذَا خَرَجَ رَسُولُ اللَّهِ صلى الله عليه وسلم إِلَى الْغَزْوِ تَخَلَّفُوا عَنْهُ، وَفَرِحُوا بِمَقْعَدِهِمْ خِلاَفَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَإِذَا قَدِمَ رَسُولُ اللَّهِ صلى الله عليه وسلم اعْتَذَرُوا إِلَيْهِ وَحَلَفُوا، وَأَحَبُّوا أَنْ يُحْمَدُوا بِمَا لَمْ يَفْعَلُوا، فَنَزَلَتْ ‏{‏لاَ يَحْسِبَنَّ الَّذِينَ يَفْرَحُونَ‏}‏ الآيَةَ‏.‏