إِنَّ الْأَبْرَارَ لَفِي نَعِيمٍ
The righteous are surely in bliss.
Inna is the emphatic particle governing the accusative; al-abrar is its accusative noun; the prefixed lam adds emphasis; fi na‘im forms the predicate phrase. The second verse repeats the same construction with the wicked.
وَإِنَّ الْفُجَّارَ لَفِي جَحِيمٍ
And the wicked are surely in Hellfire.
Parallel syntax alone would not suffice: the clauses are also both declarative and meaningfully contrasted. These features jointly support their connection.