The Quran

يا أَيُّهَا النَّبِيُّ قُل لِأَزواجِكَ وَبَناتِكَ وَنِساءِ المُؤمِنينَ يُدنينَ عَلَيهِنَّ مِن جَلابيبِهِنَّ ۚ ذٰلِكَ أَدنىٰ أَن يُعرَفنَ فَلا يُؤذَينَ ۗ وَكانَ اللَّهُ غَفورًا رَحيمًا

Muhammad Asad

O Prophet! Tell thy wives and thy daughters, as well as all [other] believing women, that they should draw over themselves some of their outer garments [when in public]: this will be more conducive to their being recognized [as decent women] and not annoyed.¹ But [withal,] God is indeed much-forgiving, a dispenser of grace!²

Cf. the first two sentences of 24:31 and the corresponding notes 37 and 38.
The specific, time-bound formulation of the above verse (evident in the reference to the wives and daughters of the Prophet), as well as the deliberate vagueness of the recommendation that women "should draw upon themselves some of their outer garments (min jalabibihinna)" when in public, makes it clear that this verse was not meant to be an injunction (hukm) in the general, timeless sense of this term but, rather, a moral guideline to be observed against the ever-changing background of time and social environment. This finding is reinforced by the concluding reference to God's forgiveness and grace.