the Prophet proceeded to Tabuk personally at the head of 30...

the Prophet proceeded to Tabuk personally at the head of 30,000 strong army and, returned to Madina without fighting and without encountering the enemy. In view of all this the Prophet apprehended very serious danger and for this reason he organized, after return to Madina, an army consisting of the Muhajirs and the Ansar, which included distinguished persons like Abu Bakr, Umar, Abi 'Ubaydah, Sa'd Waqqas etc.

In fact he ordered that all those Muhajirs who had migrated to Madina earlier than others should participate…