When the city of Damascus was conquered by the Muslims, Hazrat Abu Ubaidah (radhiyallahu ‘anhu) – the commander of the Muslim army – appointed Hazrat Sa’eed bin Zaid (radhiyallahu ‘anhu) as the governor over the city of Damascus.
Thereafter, Hazrat Abu Ubaidah (radhiyallahu ‘anhu) proceeded with his army towards Jordan. Upon reaching Jordan, they encamped there and began making preparations to face the enemy. Hazrat Abu Ubaidah (radhiyallahu ‘anhu) appointed Hazrat Khaalid bin Waleed and Hazrat Yazeed bin Abu Sufyaan (radhiyallahu ‘anhuma) as the main generals over the army.
When Hazrat Sa’eed bin Zaid (radhiyallahu ‘anhu) was informed that the Muslim army will soon be engaging in battle against the disbelievers, a strong desire entered his heart to join the Muslim army and sacrifice his life for the sake of Allah Ta’ala.
Overcome by this strong desire, he wrote a letter to Hazrat Abu Ubaidah (radhiyallahu ‘anhu) in which he expressed his eagerness to join the Jihaad and he also requested to be relieved of his position as governor over Damascus.
After praising Allah Ta’ala and conveying salaam, he wrote the following in the letter to Hazrat Abu Ubaidah (radhiyallahu anhu): “In regard to taking part in Jihaad, I cannot remain behind and give you and your companions preference over myself, especially when Jihaad is the means for me gaining the pleasure (and close proximity) of my Rabb. Therefore, as soon as you receive this letter of mine, please appoint someone in my place who has more desire to manage this responsibility than myself, as I will soon be joining the army, insha Allah.”
When the letter of Hazrat Sa’eed bin Zaid (radhiyallahu ‘anhu) reached Hazrat Abu Ubaidah (radhiyallahu ‘anhu), he remarked: “He (Sa’eed) is determined to leave his position (and join the Jihaad, hence we cannot stop him now).” He then called Hazrat Yazeed bin Abu Sufyaan (radhiyallahu ‘anhu, his main general) and instructed him to appoint someone as governor over Damascus, in place of Hazrat Sa’eed (radhiyallahu ‘anhu). (Ar Riyaadhun Nadhrah fi Manaaqibil ‘Ashrah 4/343)