How large was the Muslim army in the Battle of Tabuk?

Sources state that the number of the Muslim army in the Battle of Tabuk was thirty thousand men, and it was also said to be seventy thousand, and forty thousand. Ibn Ishaq, Al-Waqidi, and Ibn Sa'd definitively stated that their number was thirty thousand, while Al-Hakim narrated from Abu Zur'ah that their number was seventy thousand. The narrations can be reconciled by understanding that whoever stated thirty thousand did not count the followers, while whoever stated seventy thousand counted both the followers and the followed. As for whoever stated forty thousand, it might have been a rounding up of a fraction. The number of horses was ten thousand.