Both are revelation from Allah, but the Quran is Allah's speech in its exact wording and meaning, transmitted by mass narration (tawatur), recited in salah as an act of worship, inimitable in its wording, and governed by the special rulings of the mushaf. A hadith qudsi is a report in which the Prophet (ﷺ) attributes the meaning to his Lord — "Allah says…" — but, on the more common definition, it is conveyed in the Prophet's own wording; it is not recited in prayer and is not a miracle of eloquence. Hadith qudsi are also transmitted like other hadith, so they range from authentic to weak and each must be checked, whereas the Quran is not subject to that. The Quran's inimitability is part of what sets it apart: Allah challenged mankind to "produce a surah the like of it" (Quran 2:23) and declared that even if mankind and jinn combined they could not produce its like (Quran 17:88). Both are ultimately wahy, since Allah says of the Prophet (ﷺ): "Nor does he speak from his own desire; it is only a revelation revealed" (Quran 53:3-4).
Q&A · Quran
What is the difference between the Quran and a hadith qudsi?
Evidence — the daleel
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Informational, not a personal fatwa. Consult a qualified scholar for rulings on your situation.