إِن تُبْدُوا شَيْئًا أَوْ تُخْفُوهُ فَإِنَّ اللَّـهَ كَانَ بِكُلِّ شَيْءٍ عَلِيمًا (If you disclose any thing, or conceal it, Allah is All-Knowing about everything - 33:54). It has been repeated again in this verse that Allah Ta’ ala knows even the intents and thoughts hidden in the hearts. So whether you disclose or conceal, Allah Ta’ ala knows it all. What is being emphasized here is that one should not let any doubt or suspicion enter one's mind or heart about the above-stated rules, and must avoid any violation of these rules.
The issue of Hijab for women, out of the three injunctions in the above mentioned verse, needs some further elaboration which is being given below.