The Quran

لا جُناحَ عَلَيهِنَّ في آبائِهِنَّ وَلا أَبنائِهِنَّ وَلا إِخوانِهِنَّ وَلا أَبناءِ إِخوانِهِنَّ وَلا أَبناءِ أَخَواتِهِنَّ وَلا نِسائِهِنَّ وَلا ما مَلَكَت أَيمانُهُنَّ ۗ وَاتَّقينَ اللَّهَ ۚ إِنَّ اللَّهَ كانَ عَلىٰ كُلِّ شَيءٍ شَهيدًا

Muhammad Asad

[However,] it is no sin for them¹ [to appear freely] before their fathers, or their sons, or their brothers, or their brothers' sons, or their sisters' sons, or their womenfolk, or such [male slaves] as their right hands may possess. But [always, O wives of the Prophet,²] remain conscious of God - for, behold, God is witness unto everything.

I.e., the wives of the Prophet (connecting with the injunction, in verse 53 above, that they should be spoken to "from behind a screen").
This interpolation is conditioned by the feminine gender of the subsequent plural imperative ittaqina.