Is "He who looks at what is unlawful for him, Allah Almighty will deny him the sight of His Noble Face on the Day of Resurrection and cast him into Hellfire" a Prophetic Hadith, and if not, what is its origin?

There is no known hadith with this wording or meaning, and we do not know of any origin for it from the Prophet, peace and blessings be upon him, nor from any of his Companions. It has been mentioned in some books of admonition as a statement attributed to God to David, peace be upon him, warning him against looking at what is unlawful for him, and threatening punishment and deprivation from seeing God for those who do so. However, it is an unverified statement whose narrator and source are unknown.