Jamiat Tirmidhi: Hadith 1593

That the Messenger of Allah (ﷺ) said: "The best companions are four, the best Saraya (military unit) is four hundred, the best army is four thousand, and twelve thousand will not be beaten due to being too few."

This Hadith is Hasan Gharib, it was not narrated with a chain by anyone important besides Jarir bin Hazim, and this Hadith was only reported from Az-Zuhri, from the Prophet (ﷺ) in Mursal form. Hibban bin 'Ali Al-'Anazi reported it from 'Uqail, from Az-Zuhri, from 'Ubaidullah, from 'Ibn Abbas, from the Prophet (ﷺ), and Al-Laith bin Sa'd reported it from Sa'd, from 'Uqail, from Az-Zuhri, from the Prophet (ﷺ) in the Mursal form.