Surah 74. Al-Muddaththir, Ayah 4

Lit., "thy garments (thiyab) purify": but almost all the classical commentators point out that the noun thawb and its plural thiyab is often metonymically applied to that which a garment encloses, i.e., a person's "body" or, in a wider sense, his "self" or his "heart", or even his "spiritual state" or "conduct" (Taj al-'Arus). Thus, commenting on the above verse, Zamakhshari draws the reader's attention to the well-known idiomatic phrases tahir ath-thiyab (lit., "one who is clean in his garments") and danis ath-thiyab ("one who is filthy in his garments"), and stresses their tropical significance of "free from faults and vices" and "vicious and perfidious", respectively. Razi states with approval that "according to most of the [earlier] commentators, the meaning [of this verse] is, 'purify thy heart of all that is blameworthy'".

Possibly, in its immediate application, there is a reference to the dirt and filth which the Pagans used to throw at the Prophet to insult and persecute him.