Those, namely, these signs, are the signs of the Manifest Book (the genitive annexation conveys the [partitive] sense of min, ‘of’ [‘verses from the Manifest Book’]), [the Manifest Book] which reveals truth from falsehood.
(We recite to you some of the news of Musa and Fir`awn in truth,) This is like the Ayah,
نَحْنُ نَقُصُّ عَلَيْكَ أَحْسَنَ الْقَصَصِ
(We relate unto you the best of stories) (12:3). which means, `We tell you about things as they really were, as if you are there and are seeing them yourself.' Then Allah says:
إِنَّ فِرْعَوْنَ عَلاَ فِى الاٌّرْضِ
(Verily, Fir`awn exalted himself in the land) means, he was an arrogant oppressor and tyrant.
وَجَعَلَ أَهْلَهَا شِيَعاً
(and made its people Shiya`) means, he made them into different classes, each of which he used to do whatever he wanted of the affairs of his state.
يَسْتَضْعِفُ طَآئِفَةً مِّنْهُمْ
(weakening a group among them. ) This refers to the Children of Israel, who at that time were the best of people, even though this tyrant king overpowered them, using them to do the most menial work and forcing them to hard labor night and day for him and his people. At the same time, he was killing their sons and letting their daughters live, to humiliate them and because he feared that there might appear among them the boy who would be the cause of his destruction and the downfall of his kingdom. So Fir`awn took precautions against that happening, by ordering that all boys born to the Children of Israel should be killed, but this precaution did not protect him against the divine decree, because when the term of Allah comes, it cannot be delayed, and for each and every matter there is a decree from Allah. Allah says:
(And We made the people who were considered weak) until His saying;
(they erected) (7:137). And Allah said:
كَذَلِكَ وَأَوْرَثْنَـهَا بَنِى إِسْرَءِيلَ
(Thus and We caused the Children of Israel to inherit them) (26: 59). Fir`awn hoped that by his strength and power he would be saved from Musa, but that did not help him in the slightest. Despite his great power as a king he could not oppose the decree of Allah, which can never be overcome. On the contrary, Allah's ruling was carried out, for it had been written and decreed from past eternity that Fir`awn would meet his doom at the hands of Musa.
Maududi - Sayyid Abul Ala Maududi - Tafhim al-Qur'an