The Quran

118

وَعَلَى الثَّلاثَةِ الَّذينَ خُلِّفوا حَتّىٰ إِذا ضاقَت عَلَيهِمُ الأَرضُ بِما رَحُبَت وَضاقَت عَلَيهِم أَنفُسُهُم وَظَنّوا أَن لا مَلجَأَ مِنَ اللَّهِ إِلّا إِلَيهِ ثُمَّ تابَ عَلَيهِم لِيَتوبوا ۚ إِنَّ اللَّهَ هُوَ التَّوّابُ الرَّحيمُ

Mir Aneesuddin

and to the three who were left behind¹ (from going to the battle and whose condition became bad) to the extent that the earth, inspite of its spaciousness, became constrained on them and their souls (too) became constrained on them and they thought that there is no refuge from Allah except (in going) to Him. Then He turned to them (mercifully) that they may repent, Allah is certainly the Accepter of repentance, the Merciful. (R 14)

The three left behind during the expedition of Tabuk were Kab bin Malik, Halal bin Umayya and Mararah bin Rabi, they were all from Madina. Because they had not gone with the army of the muslims they were cut off from the community for fifty days. after which Allah finally forgave them.