Undoubtedly, Quran is necessarily a decisive word.
This is a serious narration
this is indeed a Decisive Word
Surely it is a decisive word
That it truly is a word/statement (of) judgment/partition (decisive)
this scripture is not…
Indeed the Qur’an is a decisive Word
Surely, the Qur'an is a decisive word
This is indeed a decisive (i.e., absolute) commandment
(That) verily, this (Qur'an) is a decisive word
Verily! This (the Quran) is the Word that separates (the truth from falsehood, and commands strict legal laws for mankind to cut the roots of evil)