Umar left instructions for his successor that no change should be made in the Governors appointed by him for one year and that thereafter his successor was free to make whatever changes he deemed necessary in public interest.
When Uthman became the Caliph, Mugheera b Shu'ba was the Governor of Kufa. True to the instructions of Umar, Uthman allowed the (Governors appointed by Umar to continue in their office. After the expiry of one year, Uthman deposed Mugheera and appointed Sa'ad b Abi Waqas as the Governor of Kufa.
"When a person dies, his works end, except for three: ongoing charity, knowledge that is benefited from, and a righteous child who prays for him."
Prophet Mohammed (PBUH)
"The best of what a man leaves behind are three: a righteous child who supplicates for him, ongoing charity the reward of which reaches him, and knowledge that is acted upon after him."
Sunan Ibn Mājah
"Every day two angels come down from Heaven and one of them says, 'O Allah! Compensate every person who spends in Your Cause,' and the other (angel) says, 'O Allah! Destroy every miser.'"
Sahih Bukhari