Quran

These separated letters were stated at the beginning of some Surahs to assert the inimitability of the Quran, and the fact that mankind is incapable of matching its eloquent level even though it is made up of these letters by which they speak. Therefore; each Surah that begins with these letters mentions the supremacy, inimitability, and greatness of the Quran, and this is known by induction. Ibn Kathir: 1/36-37.
Question: What is the link between the separated letters and induction of greatness and inimitability of the Quran?

Allah does not say guidance for a specific interest or thing. Rather, it is left generalized because the Quran is a general guidance to all benefits of this life and the Hereafter. The Quran is a guidance for servants in all issues, both fundamental and incidental; it clearly separates truth from falsehood, sound from weak, and shows them how to follow the paths that are beneficial to them in this life and the Hereafter. Al-Saadi: 40.
Question: How it can be inferred from this verse that guidance of the Quran is inclusive of all benefits of both this life and the Hereafter?

Believing in the unseen is a role of the heart, establishing prayer is a role of the body,(and spend out of what We have provided for them) is a role of wealth, which is all apparent. Al-Qurtubi: 1/274.
Question: This verse combines three aspects of righteousness, what are they?

Allah does not say that they "do" or "perform" the prayer, because it is not sufficient to merely perform its outward form. Establishing prayer means establishing its outward form completely, fulfilling its pillars, obligations, and conditions, as well as establishing it inwardly by performing its essence, which is attentiveness of the heart, and reflecting on what one says and acts in it. Al-Saadi: 41.
Question: The word (Establish) is used for performing prayer. Why?

(Out of) is used to indicates "some" in order to signal to them that only a fraction of their wealth is required for spending, which would not cause them any harm or overburden. In fact, they would gain a reward, and their needy brethren would benefit. (Of what We have provided for them) is an indication that the wealth in your possession is not gained by your own power, but rather it is the provision of Allah that He has bestowed upon you. Just as Allah has favored you over many of His servants [by giving you this wealth], thank Him by giving out some of what He has bestowed upon you. Al-Saadi: 41.
Question: What is the significance of using (out of)?

Believing in the unseen entails spending because provision from Allah is, in fact, part of the unseen, and therefore; when the servant is certain of receiving compensation from Allah for his spending, he will spend even more; and when he extends his favors to others, his succession on earth will be fulfilled, his authority will be expanded, and more bountiful provision will come his way. Al-Biqai: 1/30.
Question: Why does spending depend on believing in the unseen?

Certainty is the highest level of knowledge with which there is no doubt. Ibn Atiyah: 1/86.
Question: The more certainty in believing in the Hereafter, the more deeds are exerted for it, explain in light of this verse.