Here Allah tells us about His servant and Messenger Nuh, peace be upon him, who was the first Messenger sent by Allah to the people of earth after they started to worship idols. Allah sent him to forbid that and to warn people of the consequences of idol worship. But his people belied him and continued their evil practice of worshipping idols besides Allah. Allah revealed that their disbelieving in him was akin to disbelieving in all the Messengers, So Allah said:
(The people of Nuh belied the Messengers. When their brother Nuh said to them: "Will you not have Taqwa") meaning, `do you not fear Allah when you worship others instead of Him'
(I am a trustworthy Messenger to you.) means, `I am the Messenger of Allah to you, faithfully fulfilling the mission with which Allah has sent me. I convey the Messages of my Lord to you, and I do not add anything to them or take anything away from them.,
(So have Taqwa of Allah, and obey me. No reward do I ask of you for it;) means, `I do not want any payment for the advice I give you; I will save my reward for it with Allah. '
(So have Taqwa of Allah, and obey me.) `It is clear to you that I am telling the truth and that I am faithfully fulfilling the mission with which Allah has entrusted me.'