Tafseer Ibn Kathir of SABA' [39]

39. Say: ”Truly, my Lord expands the provision for whom He wills of His servants, and (also) restricts (it) for him...'') means, according to His wisdom, He gives a lot of provision to one, and gives very little to another. He has great wisdom in doing so, which cannot be comprehended by anyone but Him. This is like the Ayah:

(See how We favor one above another, and verily, the Hereafter will be greater in degrees and greater in favor.) (17:21). This means that just as there are differences between them in this world -- where one may be poor and in straitened circumstances while another is rich and enjoys a life of plenty -- so they will be in the Hereafter. There one will reside in apartments in the highest levels of Paradise, whilst another will be in the lowest levels of Hell. As the Prophet said, describing the best of people in this world:

(He truly succeeds who becomes Muslim and is given just enough provision and Allah makes him content with what He has given.)'' It was recorded by Muslim.

(39 cont. - and whatsoever you spend of anything, He will replace it.) means, `whatever you spend in the ways that He has commanded you and permitted you, He will compensate you for it in this world by giving you something else instead, and in the Hereafter by giving you reward.' It was reported that the Prophet said:

(Allah says: ”Spend, I will spend on you.'') In another Hadith it is reported that every morning, two angels come, and one says, ”O Allah, bring destruction upon the one who withholds (does not spend).'' The other one says, ”O Allah, give compensation to the one who spends.'' And the Messenger of Allah said:

(Spend, O Bilal, and do not fear that the One Who is on the Throne will withhold from you. )