The ulterior motive behind this was to amass wealth and to grasp power. Imam Ali (a) had appointed him as the Governor of Azarbaijan. He started collecting and procuring wealth by every means possible. When this was reported to Imam Ali (a), he wrote the following letter to Ash’ath: On receipt of this letter he wanted to abscond with the wealth so amassed but good counsels prevailed upon him and he was persuaded by Hujr bin Adi Kindi to got to Imam Ali (a). When his accounts were audited he had to surrender 400,000 dirhams.
Verily, you have neither been entrusted with the governorship so that you amass wealth nor is it a tasty and juicy morsel to be swallowed up. On the contrary it is a trust committed to your care and trust. Its responsibility lies upon your shoulders.
Your Amir (meaning Imam Ali himself) has appointed you as a shepherd and a guardian of the people. You have no right to do as you like and to act independently without seeking his advice and permission. In all important affairs of the State and the public, your decisions must be based on true facts and sound reasons. In your control and custody there is one of the treasuries of Allah, you are only a treasurer, you have no right to make personal use of any part of this wealth, it is your duty to pass it on to whom it belongs.
I hope you will not give me a chance to prove myself a hard task-master and a harsh administrator. May you see the light.