“Al-ḥaqqu min rabbik”
“The truth is from your Lord.” (al-Baqarah 2:147, excerpt)
The expression can be explicated as “this is the truth from your Lord,” with an understood demonstrative pointing to the matter already discussed.
Yet the wording itself also expresses the essential predicate: truth comes from God. The possible reconstruction supplies a discourse link; it does not mean the Qur’anic expression is deficient.
An implied subject or demonstrative should be proposed when the before-and-after context supports the particular reference. Adding “this” to every similar sentence automatically would be methodologically unsound.