Tafsir of Ya seen 36:74

They took these gods, hoping to be strengthened by them and to find support in their status. Yet the matter is the opposite of what they estimated; for they are a host prepared for their gods, "brought forth" [to serve them], defending them and becoming angry on their behalf. Yet the gods have no ability or power to grant victory.

Or, they took them so that they might help them before Allah and intercede for them. The matter is the opposite of what they imagined, for on the Day of Resurrection, they are a host prepared for them, brought forth for their punishment, because they are made fuel for the Fire.

It was recited as fa-lā yaḥzunka (with a fatḥah on the yā’) and yuḥzinuka (with a ḍammah), from ḥazanahu and aḥzanahu. The meaning is: Do not let their denial, their harm, and their harshness concern you, for We know what they conceal of their enmity toward you, "and what they proclaim." We will requite them for it. It is fitting for one like you to find solace in this threat, and to bring to mind the image of his state and their state in the Hereafter, so that anxiety may dissipate from him and grief may not overwhelm him.

If you ask: What do you say regarding one who claims that if a reader recites anna naʿlamu (with a fatḥah), his prayer is invalidated, and if he believes in the meaning it conveys, he commits disbelief?

I say: There are two aspects to this:

1. It is based on the omission of the lām of causation (taʿlīl), which is frequent in the Qur’an, poetry, and all speech, and is a consistent analogy. Its meaning is the same as the kasrah (i.e., inna). Upon this is the talbiyah of the Messenger of Allah (ﷺ): "Indeed, all praise and grace are Yours (inna al-ḥamda...)." Abu Hanifa recited it with kasrah, and al-Shafi‘i with fatḥah, and both are for the purpose of causation.
2. It is a substitute (badal) for "their saying." It is as if it were said: "Do not let their speech grieve you: [namely] that We know what they conceal and what they proclaim." This meaning holds even with the kasrah if you make it the object of the verb "saying."

Thus, it has become clear that the connection of grief to Allah’s knowledge—or the lack thereof—does not revolve around the kasrah or fatḥah of inna. Rather, it revolves around your interpretation. If you recite it with fatḥah, you distinguish it by interpreting it as causation and not as a substitute, just as you distinguish it by interpreting it as causation when you recite it with kasrah and not as an object.

Furthermore, if that speaker interprets it—whether with kasrah or fatḥah—in a way that makes the matter grave, there is nothing in it but the prohibition of the Messenger of Allah (ﷺ) from grieving, based on the fact that Allah knows their secrets and their public declarations. The prohibition of that does not necessitate anything [of disbelief]. Do you not see His saying: "Do not be a supporter of the disbelievers" (28:86), "Do not be of the polytheists" (28:87), and "Do not invoke with Allah another deity" (28:88)?