Tafsir of Al-Isra 17:9

{لِلَّتِي هِيَ أَقْوَمُ} "To that which is most upright": meaning the state which is the most upright and sound of states. Or it refers to the creed (milla), or the path (tariqa).

Wherever you estimate the omitted noun to be, you will not find with its explicit mention the taste of eloquence that you find with its omission. This is because the ambiguity of the described noun—achieved by omitting it—carries a grandeur that is lost when it is made explicit.

It is also recited: {وَيُبَشِّرَ} (wa-yubashshira) with the lightened form (takhfif).

If you ask: How is it that He mentioned the righteous believers and the disbelievers, but did not mention the sinners (al-fasaqa)?

I say: People at that time were either pious believers or polytheists. The proponents of the "position between the two positions" (al-manzila bayn al-manzilatayn) only emerged after that.

If you ask: Upon what is {وَأَنَّ الَّذِينَ لَا يُؤْمِنُونَ} (and that those who do not believe) conjoined?

I say: It is conjoined to {أَنَّ لَهُمْ أَجْرًا كَبِيرًا} (that they have a great reward), in the sense that He gave the believers two pieces of good news: one regarding their reward, and one regarding the punishment of their enemies. It is also permissible that the meaning is: "And He informs that those who do not believe are being punished."

{وَيَدْعُ الْإِنسَانُ بِالشَّرِّ دُعَاءَهُ بِالْخَيْرِ ۖ وَكَانَ الْإِنسَانُ عَجُولًا} "And man invokes evil as he invokes good, and man is ever hasty."