48. This is not a mere statement of a fact, but it is a link of the same argument which is being put forward from the very beginning of the Surah. The argument is this: Islam has been the real and original religion of all the Prophets from Noah to Jesus (peace be upon them all), because all of them brought and taught the same doctrines of Tauhid and the Hereafter. On the contrary, all the other religions are the perversions of the real and original religion, which has been tampered with in many ways. Therefore, those who are following the perverted religions are in the wrong and not the Prophet (peace be upon him) who is inviting them to the real and original religion.
49. There is a gap between (verses 53 and 54), which has been left to the listener to fill, because the background of the whole discourse itself helps to fill it. Five years had passed since the Prophet (peace be upon him) had been inviting his people to the original religion. He had left no stone unturned to convince them by reasoning and by historical evidence that his message was based on the truth. His people had seen the practical results of the acceptance of his message and had witnessed his own high character which was by itself a guarantee that he was a trustworthy man. But in spite of all this, his people were rejoicing in their erroneous beliefs which they had inherited from their forefathers. This was not all. They had become his bitter enemies and were trying to defeat him and his message by every wicked machination.
After filling the gap, the meaning of (verse 51) becomes quite clear. It does not mean that the Prophet (peace be upon him) should give up his preaching and leave the disbelievers to themselves. This way of address has been employed to shake and rouse the disbelievers. This verse warns them to realize that the time was coming near when they would see for themselves that the Messenger was in the right and they were in the wrong.