210. The three on whom the verdict was deferred.

In verse 9:118 of the Quran Allah talks about three persons whom He forgives.

The Tabook war was one of the most, critical battles that was fought during those days..Prophet Muhammad had ordered every one take part in the battle. But three of the comrades of Prophet Muhammad delayed their departure, with a intention to join Prophet Muhammad a little later, but never made it. 

Hence Prophet Muhammad ordered other muslims cut all relationships with them 

The three later regretted much of their act and Allah forgave them. This is what is mentioned in this verse of the Quran.To know more in detail about this incident refer to Hadith Book Bukhari:4418, 4676,4677, 6690.