Tafsir of Al-Hadeed 57:7-8

{...and spend out of that in which He has made you successors}

It means that the wealth in your hands is, in reality, the wealth of Allah—by His creation and origination of it. He has merely entrusted it to you, granted you the enjoyment of it, and made you successors in managing it. Therefore, it is not truly your wealth; you are in it only like agents and deputies. So, spend from it in the rights of Allah, and let spending from it be easy for you, just as it is easy for a man to spend from the wealth of another when he has been given permission to do so.

Alternatively, it means He has made you successors to those who were before you regarding what is in your hands, by bequeathing it to you. So, take a lesson from their state, as it moved from them to you, and it will move from you to those who come after you. Do not be stingy with it, and benefit yourselves by spending from it.

{What is the matter with you that you do not believe}

This is a state (ḥāl) derived from the meaning of the verb in "What is the matter with you" (mā lakum), just as you say: "What is the matter with you standing?" (māluka qāʾiman), meaning: "What are you doing while standing?" That is: "What is the matter with you, being disbelievers in Allah?"

The wāw in {and the Messenger invites you} is the wāw of state (wāw al-ḥāl), so they are two nested states. It has also been recited: "What is the matter with you that you do not believe in Allah and His Messenger, while the Messenger invites you?" The meaning is: What excuse do you have for abandoning faith when the Messenger is inviting you to it, alerting you to it, and reciting to you the Book that speaks with proofs and arguments?

Before that, Allah had already taken your covenant to believe: by installing intellects within you, setting up evidences for you, enabling you to reflect, and removing your excuses. Since no excuse remains for you after the evidences of the intellects and the warning of the Messenger, what is the matter with you that you do not believe?

{if you are believers}

...in any cause [for belief]; for this cause [the Messenger and the proofs] has no equal. It has also been recited as "He took your covenant" (akhadha mīthāqakum), in the active voice, referring to Allah, the Almighty and Exalted.

{It is He who sends down upon His Servant verses of clear evidence that He may bring you out from darknesses into the light. And indeed, Allah is to you Kind and Merciful.}