Prophet Abraham - 14:11
"And their messengers said to them: "Surely we are human beings like you. But Allah chooses whom He wills from among His servants and bestows favor upon him. It is impossible for us to bring you a certificate of authority without Allah´s permission. Believers should trust in Allah."
Why a human messenger?
The Night Journey/17:95
"Say: "If there were angels inhabiting the earth, We would have sent to them an angel from heaven as a messenger."