25:1
Blessed is He who sent down the criterion to His servant, that it may be an admonition to all creatures;-
In Qurʾānic interpretation, the term criterion may also be translated as “divide” or “boundary,” reflecting its dual meaning: that which distinguishes and that by which distinctions are made. It is described in this manner because it separates believers from disbelievers and truth from falsehood, while also instructing believers in how to live by clearly defining what is lawful and what is prohibited (Q). In this verse, al-Furqān is another name for the Qurʾān. A similar usage appears in Qurʾān 21:48, where Moses and Aaron are described as having been given a furqān, understood more broadly as a form of divine revelation (Q).
Nasr, Seyyed Hossein; Dagli, Caner K.; Dakake, Maria Massi; Lumbard, Joseph E.B.; Rustom, Mohammed. The Study Quran (p. 890). HarperCollins. Kindle Edition.