In this reading, the word jazāʾan is a circumstantive and al-ḥusnā refers to Paradise.
جَزَاءُ الحُسْنَى
jazāʾu l-ḥusnā
"He will have the reward for the best actions" or "He will have a reward: the Best (Abode)"
In this reading, jazāʾ is annexed to al-ḥusnā, which refers to the people's good traits and acts. The latter word may also be an appositive, and the tanwin was elided.
Explication
These readings amount to the same meaning, or provide complementary meanings [al-Mahdawi].
He has revealed to you ˹O Prophet˺ the Book in truth, confirming what came before it, as He revealed the Torah and the Gospel
Explication
These readings amount to the same meaning, or provide complementary meanings [al-Mahdawi].