Messenger selection process
[38:45] Remember also our servants Abraham, Isaac, and Jacob. They were resourceful, and possessed vision. [38:46] We bestowed upon them a great blessing: awareness of the Hereafter. [38:47] They were chosen, for they were among the most righteous. [38:48] Remember Ismail, Elisha, and Zal-Kifl; among the most righteous.
[6:124] When a powerful proof comes to them, they say, "We will not believe, unless we are given what is given to GOD's messengers!" GOD knows exactly who is best qualified to deliver His message. Such criminals will suffer debasement at GOD, and terrible retribution as a consequence of their evil scheming.
[21:7] We did not send before you except men whom we inspired. Ask those who know the scripture, if you do not know.
 
Messengers are just humans…
[25:7] And they said, "How come this messenger eats the food and walks in the markets? If only an angel could come down with him, to serve with him as a preacher!”
[14:11] Their messengers said to them, "We are no more than humans like you, but GOD blesses whomever He chooses from among His servants. We could not possibly show you any kind of authorization, except in accordance with GOD's will. In GOD the believers shall trust.
[18:110] Say, "I am no more than a human like you, being inspired that your god is one god. Those who hope to meet their Lord shall work righteousness, and never worship any other god beside his Lord."
[7:188] Say, "I have no power to benefit myself, or harm myself. Only what GOD wills happens to me. If I knew the future, I would have increased my wealth, and no harm would have afflicted me. I am no more than a warner, and a bearer of good news for those who believe.”
 
They have to go through the hardship and be tested like any other believer. They don’t get a free pass. 
[2:214] Do you expect to enter Paradise without being tested like those before you? They were tested with hardship and adversity, and were shaken up, until the messenger and those who believed with him said, "Where is GOD's victory?" GOD's victory is near.
Victory, Ultimately, Belongs to the Believers
[12:110] Just when the messengers despair, and think that they had been rejected, our victory comes to them. We then save whomever we choose, while our retribution for the guilty people is unavoidable.
 
Did the messengers make mistakes?
60:1 - Abraham prayed for forgiveness for this father
21:87 - Jonah abandoned his mission
12:42 - Joseph implored his prison mate to get out 
28:15 Moses killed someone
7:22 - Adam approached the tree
38:31 - Solomon got distracted with his horses 
All creatures have committed the original sin
[35:45] If GOD punished the people for their sins, He would not leave a single creature on earth. But He respites them for a predetermined interim. Once their interim is fulfilled, then GOD is Seer of His servants.
 
No distinction among God’s messengers
You Shall Not Make Any Distinction Among God's Messengers [2:285] The messenger has believed in what was sent down to him from his Lord, and so did the believers. They believe in GOD, His angels, His scripture, and His messengers: "We make no distinction among any of His messengers." They say, "We hear, and we obey.* Forgive us, our Lord. To You is the ultimate destiny."
 
God Knows We Don't
[17:55] Your Lord is the best knower of everyone in the heavens and the earth. In accordance with this knowledge, we preferred some prophets over others. For example, we gave David the Psalms.
 
Muhammad was just a messenger like the messengers before him
[3:144] Muhammad was no more than a messenger like the messengers before him. Should he die or get killed, would you turn back on your heels? Anyone who turns back on his heels, does not hurt GOD in the least. GOD rewards those who are appreciative.
 
Muhammad had the same shortcomings as any other human or messenger
[48:1] We have bestowed upon you (O Messenger) a great victory. [48:2] Whereby GOD forgives your past sins, as well as fu