Allah says, ‘O Muhammad, tell your people who disbelieve in you,’

“a similitude; the Dwellers of the Town, when there came Messengers to them.”

In the reports that he transmitted from Ibn ‘Abbas, Ka*b Al-Ahbar and Wahb bin Munabbih - Ibn Ishaq reported that it was the city of Antioch, in which there was a king called Antiochus the son of Antiochus the son of Antiochus, who used to worship idols. Allah sent to him three Messengers, whose names were Sadiq, Saduq and Shalum, and he disbelieved in them.’ It was also narrated from Buraydah bin Al-Husayb, ‘Ikrimah, Qatadah and Az-Zuhri that it was Antioch. Some of the Imams were not sure that it was Antioch, as we shall see below after telling the rest of the story, if Allah wills.

“When We sent to them two Messengers, they denied them both; so We reinforced them with a third, and they said: "Verily, we have been sent to you as Messengers."”

means, they hastened to disbelieve in them.

“so We reinforced them with a third,” means, ‘We supported and strengthened them with a third Messenger.’ Ibn Jurayj narrated from Wahb bin Sulayman, from Shu'ayb Al-Jaba’i, “The names of the first two Messengers were Sham ‘an and Yuhanna, and the name of the third was Bulus, and the city was Antioch (Antakiyah).

“and they said” means, to the people of that city,

“Verily, we have been sent to you as Messengers.”

meaning, ‘from your Lord Who created you and Who commands you to worship Him Alone with no partners or associates.’ This was the view of Abu Al-‘Aliyah. Qatadah bin Di'amah claimed that they were messengers of the Messiah, peace be upon him, sent to the people of Antioch.

“They said: "You are only human beings like ourselves..."”
means, ‘so how could you receive revelation when you are just human beings like us, and you are not angels?’ This is the same doubt that was raised by all nations who denied their Messengers. Allah says:

“Has not the news reached you, of those before you, the people of Nuh, and ‘Ad, and Thamud? And those after them? None knows them but Allah. To them came their Messengers with clear proofs, but they put their hands in their mouths and said: "Verily, we disbelieve in that with which you have been sent, and we are really in grave doubt as to that to which you invite us." Their Messengers said: "What! Can there be a doubt about Allah, the Creator of the heavens and the earth? He calls you that He may forgive you of your sins and give you respite for a term appointed." They said: "You are no more than human beings like us! You wish to turn us away from what our fathers used to worship. Then bring us a clear authority." Their Messengers said to them: "We are no more than human beings like you, but Allah bestows His grace to whom He wills of His servants. It is not ours to bring you an authority (proof) except by the permission of Allah. And in Allah let the believers put their trust."” (14:9-11).

“and the Most Gracious has revealed nothing. You are only telling lies.”

“The Messengers said: "Our Lord knows that we have been sent as Messengers to you,"”

meaning, the three Messengers answered them saying: ‘Allah knows that we are His Messengers to you. If we were lying, He would have taken the utmost vengeance against us, but He will cause us to prevail and will make us victorious against you, and you will come to know whose will be the happy end in the Hereafter.” This is like the Ayah:

“Say: "Sufficient is Allah for a witness between me and you. He knows what is in the heavens and on earth." And those who believe in falsehood, and disbelieve in Allah, it is they who are the losers.” (29:52)

“And our duty is only to convey plainly.”

means, ‘all we have to do is to convey to you the Message with which we have been sent; if you obey, then happiness will be yours in this world and the Hereafter, and if you do not respond, you will soon know the consequences of that.’ And Allah knows best.