[4:147] Why would God chastise you if you are thankful and believe? God is ever Thankful, Knowing.
This verse is among the verses which engender a beautiful hopefulness and powerful optimism because He has made two things, "thankfulness" (shukr) and "belief" (īmān), among the signs of protection (amān) in what is to come and these are easy and light qualities. Thankfulness is an assertion (qāla) and belief is a state (ḥāla). The way becomes easy for the servant when He is pleased with him in his words and state. Thankfulness is authentic only when one hears it from a believer rather than a disbeliever, because thankfulness indicates willing obedience (?āʿa) and this cannot be said to be true of those who do not believe.
And believe, i.e., in what comes at the end. It is as if He is explaining that salvation will only be for those who, at the end of the day, believe. The meaning of the verse, then, is that God will not chastise you with the chastisement of abiding if you are thankful in your present state and put your trust in what is to come.
It is said that if you are thankful and believe, you confirm the truth that your salvation in through God, not because of your thankfulness or your belief.
It is said thankfulness is witnessing the blessing from God and belief is seeing God in the blessing. It is as if He said, "If you witness the blessing from God, then the witnessing of this blessing will certainly not cut you off from witnessing the One who gives the blessing".
Kāna Allāh shākiran ʿalīman means Allah is ever Thankful, Knowing (Allāh shākirun ʿalīmun). The meaning of His being "thankful" is that He is the One who commends his servant and the One who calls to witness him in what he does. This is because the true sense and definition of thankfulness is praise for the one who acts in a beautiful way (muḥsin) for the beautiful action he does (iḥsān). "The servant gives thanks to God" means he praises Him for His beautiful action (iḥsān) towards him, which is His blessing to him. "God gives thanks to the servant" means that He praises [the servant] for his beautiful action (iḥsān), which is his willing obedience to Him. For truly God praises him for what he does from this willing obedience despite His knowledge of his many sins.
It is said He is thankful to him even though He knows that he will return again to his unseemly actions.
It is said He is thankful to him because He knows his weakness, and it is said He is thankful to him because He knows that he is not disobedient and that his aim is not to oppose His Lord. Rather, he sins because of the overwhelming cravings that are among the states of being human.
It is said [the servant] is thankful to Him because he knows in the state of his sins that he has a Lord who pardons him.