Abbas - Tanwîr al-Miqbâs min Tafsîr Ibn ‘Abbâs
(Lo! those who disbelieve the revelations of Allah) i.e. Muhammad (pbuh) and the Qur'an, (Allah guideth them not) to His religion, i.e. He does not guide those who do not deserve to be guided; it is also said that this means: He does not guide them to the right proof nor save them from the Fire (and theirs will be a painful doom) a severe chastisement.
(Verily, those who do not believe in Allah's Ayat,) Allah will not guide them, and theirs will be a painful punishment, meaning, the disbelievers and heretics who are known to the people as liars. The Messenger Muhammad, on the other hand, was the most honest and righteous of people, the most perfect in knowledge, deeds, faith and conviction. He was known among his people for his truthfulness and no one among them had any doubts about that - to such an extent that they always addressed him as Al-Amin (the Trustworthy) Muhammad. Thus when Heraclius, the king of the Romans, asked Abu Sufyan about the attributes of the Messenger of Allah, one of the things he said to him was, "Did you ever accuse him of lying before he made his claim'' Abu Sufyan said, "No''. Heraclius said, "He would refrain from lying about people and then go and fabricate lies about Allah''
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an
In this connection, traditions mention the names of several persons, one of whom (Jabar), according to the disbelievers of Makkah taught the Holy Prophet; however, one thing particularly noteworthy about all these persons is that they were non-Arab slaves. Whosoever he might be, the fact that he used to recite the Torah and the Gospel and had an acquaintance with the Holy Prophet, gave an opportunity to the disbelievers for spreading this false report that it was the particular slave who was the real author of the Holy Qur'an, but Muhammad (Allah's peace be upon him) presented it as the Word of God. This not only shows that his opponents were very impudent in spreading false accusations against the Holy Prophet but also that, in general, people are not just in judging the worth of their contemporaries. They were ill-treating like this that great personality who has had no parallel in history. Nevertheless, these people who had become blind in their opposition, preferred to attribute the authorship of the matchless Arabic Qur'an to a non-Arab slave who had a smattering of the Torah and the Gospel. Instead of accepting the claim of the Holy Prophet, who was an embodiment of truth, they attributed its authorship to an insignificant foreign slave.
This verse can also be rendered like this: "A Prophet does not forge any false thing but those, who do not believe in the Revelations of Allah, invent falsehoods."