God uses imperfect people:  Exodus 3:10-14 (KJ21)

¹⁰Come now therefore, and I will send thee unto Pharaoh, that thou mayest bring forth My people, the children of Israel, out of Egypt."

   
 ¹¹And Moses said unto God, "Who am I, that I should go unto Pharaoh, and that I should bring forth the children of Israel out of Egypt?"

   
 ¹²And He said, "Certainly I will be with thee; and this shall be a token unto thee that I have sent thee: when thou hast brought forth the people out of Egypt, ye shall serve God upon this mountain."

   
 ¹³And Moses said unto God, "Behold, when I come unto the children of Israel and shall say unto them, `The God of your fathers hath sent me unto you,' and they shall say to me, `What is His name?' what shall I say unto them?"

   
 ¹⁴And God said unto Moses, "I AM THAT I AM." And He said, "Thus shalt thou say unto the children of Israel, `I AM hath sent me unto you.'"