Tafsir of Al-Ahzab 33:71

He will rectify for you your deeds: By accepting them and rewarding you for them, as has been narrated on the authority of Ibn Abbas and Muqatil. It has also been said that the rectification of deeds is the success in performing them in a righteous and pleasing manner.

And He will forgive you your sins: And He will make them expiated through your uprightness in speech and action.

And whoever obeys Allah and His Messenger: Regarding the commands and prohibitions, among which are those contained in these verses.

He has indeed attained a great success: In both abodes, the magnitude of which cannot be estimated and the extent of which cannot be reached.

It is stated in al-Kashshaf that this verse—meaning "O you who have believed, fear Allah" until its end—confirms the one before it. The former was built upon the prohibition against harming the Messenger of Allah (may Allah exalt his mention and grant him peace), while this one is built upon the command to fear Allah the Exalted regarding the safeguarding of the tongue. Thus, the prohibition and the command are coupled, with the prohibition followed by what contains a warning through the story of Musa (peace be upon him), for describing his high standing before Allah the Exalted implies that He avenged him against those who harmed him. The command is followed by a profound promise, so that the deterrent against harm and the incentive to abstain from it are strengthened. So, do not be heedless of this.