لَيْسَ عَلَيْكُمْ جُنَاحٌ أَنْ تَدْخُلُوا بُيُوتًا غَيْرَ مَسْكُونَةٍ فِيهَا مَتَاعٌ لَكُمْ وَاللَّهُ يَعْلَمُ مَا تُبْدُونَ وَمَا تَكْتُمُونَ ﴿۲۹﴾ قُلْ لِلْمُؤْمِنِينَ يَغُضُّوا مِنْ أَبْصَارِهِمْ وَيَحْفَظُوا فُرُوجَهُمْ ذَلِكَ أَزْكَى لَهُمْ إِنَّ اللَّهَ خَبِيرٌ بِمَا يَصْنَعُونَ ﴿۳۰﴾

﴾29﴿ Laisa 'alaikum junaahun ann tadkhuloo buyootan ghaira maskoonatin feeha mataa'ul lakum; wallaahu ya'lamu maa tubdoona wa maa taktumoon
﴾30﴿ Qul lilmu' mineena yaghuuddoo min absaarihim wa yahfazoo furoojahum; zaalika azkaa lahum; innallaaha khabeerum bimaa yasna'oon

﴾29﴿ There is no sin upon you if you enter houses in which no one lives, and in which there is benefit for you. And Allah knows what you reveal and what you conceal
﴾30﴿ And tell the believers to lower some of their gazes and guard their private parts. That is purer for them. Indeed, Allah is All-Aware of what they do

[29] What is meant here are places where no one resides—such as shops, markets, and offices—where people enter for their needs.
In such cases, there is no need to seek permission.
[30] This third etiquette is for the believers—to control the eyes and the private parts.
The etiquette regarding the eyes is mentioned first because the eye is the main means by which an effect reaches the heart, and also because it is a source of inclination.
The phrase (مِنْ أَبْصَارِهِمْ)—the word min is connected to ghadd (lowering), and since ghadd implies reduction, the meaning becomes that a person should reduce the use of their eyes in looking.
Or min may be for partiality, and ghadd may mean to lower completely—so the meaning is to lower and turn away some of one’s looks.
In both cases, the purpose is not to let the eyes look at just anything or anywhere.
The object of the verb is not mentioned here, but religiously and culturally, it is understood that the intended meaning is to avoid looking at parts of the body that are forbidden to be exposed for both men and women.
Some looks are permitted—such as sudden accidental glances that happen without intention.
In that case, the ruling is to quickly turn the gaze away, as mentioned in an authentic hadith narrated from Jarīr ibn ‘Abdullāh (may Allah be pleased with him).
Some permissible looks also occur during medical treatment.
(يَحْفَظُوا فُرُوجَهُمْ)—what is meant by guarding the private parts is to prevent exposing them, and by extension, to also protect them from immoral acts.
Min is not mentioned here because guarding the private parts is always necessary—whether with others or alone in solitude.
Even when alone, one should not expose their private parts unnecessarily, out of modesty before the angels and before Allah, as stated in an authentic hadith.
(أَزْكَى)—means that by practicing this etiquette, the heart and body are purified from sinful thoughts and actions, as well as from disgrace and accusation.
This implies that pure and respectful interaction is achieved through these etiquettes.
(يَصْنَعُونَ)—ṣan‘ refers to an action that becomes habitual.
So for someone who has made a habit of letting their eyes wander or of exposing their private parts, this serves as a warning and correction.