Exegesis of the saying of Allah the Exalted: "And those who believe in what has been revealed to you and what was revealed before you, and in the Hereafter, they are certain."

This verse is also among their characteristics.
The verse here is conjoined to what came before it; it is a conjunction of attributes, not of entities. The default for conjoined items is that they be entities, but here the conjunction is of attributes, because those who believe in what has been revealed to you and what was revealed before you are those who believe in the unseen and establish prayer. Conjoining attributes to one another is not surprising, neither in the Qur'an nor in the language of the Arabs. Allah the Exalted said: This is a conjunction of attributes to one another.
And it is the Qur'an. We might say that it is more comprehensive than the Qur'an, based on the saying of Allah the Exalted: And it is the Qur'an and the Sunnah. From the books, such as the Torah and the Gospel.
His saying: is a prepositional phrase in the genitive case, attached to "they are certain." The word was used for emphasis; otherwise, if it were omitted and it were said , the sentence would be grammatically correct. But for the sake of emphasis, the pronoun "they" was used. And his saying: means they believe with a faith in which there is no doubt and to which no possibility of doubt can attach, because certainty is definitive knowledge. This is among their characteristics.