It is God the Lord and Creator of the universe who elected and sent Mohammad (SA) to mankind, to warn the faithless and heedless; and also to bear glad-tidings for the faithful and heedful, who will listen and repent. In other titles, Mohammad is the Messenger of God and a Mercy from Him to all.
And there never has a people been without a warner who lived among them and warned them before God's punishment came to smash them and destroy them utterly.
Then in the next verse the prophet is consoled. The soothing voice says:-
``And if they belie you, so did belie those who were before them. Their Messengers came to them with evidences, and Psalms, and Illuminating Book.''
Therefore Mohammad (SA) was not the only apostle rejected by his faithless people. Others were also belied and denied in spite of having Evidences, Psalms, and Illuminating Book.
Here in the above verse, ``Evidences'' may mean miracles and various signs that the prophets had with them to convince their people.
By ZOBUR=PSALMS the reference might be to that part of the Scriptures that consists of advices and supplicatory hymns and entreats; whereas by Illuminating Book that part of the Scriptures may be intended which consists of the commandments and instructions, and know hows.