Apposition is known as badl (بدل) in traditional Arabic grammar. In this construction, two nouns will be placed side by side, both with the same syntactic function. The two nouns must have the same case ending (grammatical case). In verse (96:16) below, the noun (96:16:1) is an apposition (badl) to (96:15:6). Both these nouns have the same case ending and are in the genitive case majrūr (مجرور). The first noun (96:15:6) is in the genitive case because of a prefixed preposition and since the two nouns are in apposition, the same case ending applies to (96:16:1).
by the forelock,
Fig 1. Apposition between two nouns in verse (96:16).