Oh you Messenger! You convey whatever has been sent down to you from your Lord, and if you didn’t do so, you didn’t have to convey His Message, and Allah is enough to protect you from mankind, indeed Allah doesn’t guide the disbelieving people.
Messengers are humans who are entitled to convey Lord's Message to the entire mankind. All the 313 Messengers from Noah to Muhammad are sent down with Adhikr to teach mankind that there is no deity except Lord and to serve Him alone as explained in verses 21: 24-25. It is told in verse 13: 40 that Messenger's responsibility is to convey the Message while Reckoning is upon Lord. There is no duty upon the Messenger except conveying the Message as explained in verse 5: 99. Adhikr is the Message for entire mankind until Doomsday. It is told in verses 33: 39-40: "Messengers who convey the Message of Lord don't fear anyone except the Lord, and Lord is sufficient as an Accountant. Muḥammad is not the father of anyone, but he is the Messenger of Lord and the last of Prophets, and Lord is the Knower of everything".
After thirty years of the last Messenger Muhammad's departure, Islam has deteriorated and his people have become the Arabic Quran reading Fujjar who are true disbelievers as explained in verses 4: 150-151. They didn’t try to learn or teach Adhikr. Instead, they started to promote and propagate the books written by the pseudo-prophets and hypocrites as explained in verses 2: 78-79 and 3: 78. So these Fujjar can never understand Adhikr and they will be never guided into the Straightpath.
Jesus will come for the second time not as a Messenger or Prophet. Instead, he will come to kill Antichrist and introduce Adhikr and Messenger Muhammad as the Mercy for the entire mankind as explained in verse 21: 107.
The one in a thousand believer holdfasts the Lord by holding Adhikr which is the Unbreakable Rope extended from Paradise into the earth as explained in verse 2: 256. He conveys It to the entire mankind, especially to the other people belonging to Messenger's community aiming to form a harmony of mankind as well as extend the lifespan of the universe. He always tries to spread the Light Adhikr whereas the Fujjar always try to extinguish It. See explanation 2: 2, 99; 3: 108 and 5: 33.