Tafsir of Fussilat 41:6

If you ask: How is His saying, "I am only a human being like you, to whom it has been revealed," an answer to their saying, "Our hearts are within coverings"?

I say: It is because he said to them: I am not an angel; I am merely a human being like you. Yet, revelation has come to me, and not to you. Thus, my prophethood is validated by the revelation coming to me while I am a human. Once my prophethood is validated, it becomes obligatory for you to follow me. Among the things revealed to me is that "your God is One God," so "take a straight course to Him"—meaning, be upright toward Him through monotheism and sincerity in worship, without veering to the right or left, and without turning toward what Satan whispers to you regarding taking patrons and intercessors. "And seek His forgiveness" for the polytheism that has preceded you. (It is also recited: "He said, I am only a human being.")

If you ask: Why, among the attributes of the polytheists, was the withholding of Zakat singled out and paired with disbelief in the Hereafter?

I say: Because a person’s wealth is the dearest thing to them; it is the twin of their soul. When one spends it in the path of Allah, it is the strongest proof of their steadfastness, their uprightness, the sincerity of their intention, and the purity of their inner self. Do you not see His saying—Exalted is He—"And the example of those who spend their wealth seeking the pleasure of Allah and as a confirmation from themselves" (Al-Baqarah: 265)? This means: they confirm their own steadfastness and provide evidence for it by spending their wealth.

The Mu'allafati Qulubuhum (those whose hearts are to be reconciled) were only won over by a morsel of worldly gain, which calmed their hostility and softened their defiance. Furthermore, the apostates after the Messenger of Allah (peace be upon him) did not manifest their rebellion except by withholding Zakat, so war was waged against them and they were fought.

In this, there is an incitement for the believers to pay Zakat and a severe warning against withholding it, as it is categorized as an attribute of the polytheists and paired with disbelief in the Hereafter.

It has also been said: The Quraysh used to feed the pilgrims and deprive those among them who believed in the Messenger of Allah. Others said: It means they do not perform the deeds that would make them pure (azkiya'), which is faith.