[He has made it] straight, to warn of severe punishment from Him and to give good tidings to the believers who do righteous deeds that they will have a good reward [i.e., Paradise]
But rather He made it straight without any contradiction or discrepancy in it, to frighten those who deny the truth of a severe punishment which awaits them from Allah, and to tell the believers who do good actions what will please them, namely that there is a good reward for them which no other reward compares with.