Texts from the Quran and from Sahih al-Bukhari and Sahih Muslim about greeting and manners. This is a collection of texts, not a ruling and not a fatwa. For your own situation, ask a qualified scholar. All topics
From the Quran
وَإِذَا حُيِّيتُم بِتَحِيَّةٍۢ فَحَيُّوا۟ بِأَحْسَنَ مِنْهَآ أَوْ رُدُّوهَآ ۗ إِنَّ ٱللَّهَ كَانَ عَلَىٰ كُلِّ شَىْءٍ حَسِيبًا
And when you are greeted with a greeting, greet [in return] with one better than it or [at least] return it [in a like manner]. Indeed, Allah is ever, over all things, an Accountant.
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ لَا تَدْخُلُوا۟ بُيُوتًا غَيْرَ بُيُوتِكُمْ حَتَّىٰ تَسْتَأْنِسُوا۟ وَتُسَلِّمُوا۟ عَلَىٰٓ أَهْلِهَا ۚ ذَٰلِكُمْ خَيْرٌۭ لَّكُمْ لَعَلَّكُمْ تَذَكَّرُونَ
O you who have believed, do not enter houses other than your own houses until you ascertain welcome and greet their inhabitants. That is best for you; perhaps you will be reminded.
لَّيْسَ عَلَى ٱلْأَعْمَىٰ حَرَجٌۭ وَلَا عَلَى ٱلْأَعْرَجِ حَرَجٌۭ وَلَا عَلَى ٱلْمَرِيضِ حَرَجٌۭ وَلَا عَلَىٰٓ أَنفُسِكُمْ أَن تَأْكُلُوا۟ مِنۢ بُيُوتِكُمْ أَوْ بُيُوتِ ءَابَآئِكُمْ أَوْ بُيُوتِ أُمَّهَٰتِكُمْ أَوْ بُيُوتِ إِخْوَٰنِكُمْ أَوْ بُيُوتِ أَخَوَٰتِكُمْ أَوْ بُيُوتِ أَعْمَٰمِكُمْ أَوْ بُيُوتِ عَمَّٰتِكُمْ أَوْ بُيُوتِ أَخْوَٰلِكُمْ أَوْ بُيُوتِ خَٰلَٰتِكُمْ أَوْ مَا مَلَكْتُم مَّفَاتِحَهُۥٓ أَوْ صَدِيقِكُمْ ۚ لَيْسَ عَلَيْكُمْ جُنَاحٌ أَن تَأْكُلُوا۟ جَمِيعًا أَوْ أَشْتَاتًۭا ۚ فَإِذَا دَخَلْتُم بُيُوتًۭا فَسَلِّمُوا۟ عَلَىٰٓ أَنفُسِكُمْ تَحِيَّةًۭ مِّنْ عِندِ ٱللَّهِ مُبَٰرَكَةًۭ طَيِّبَةًۭ ۚ كَذَٰلِكَ يُبَيِّنُ ٱللَّهُ لَكُمُ ٱلْءَايَٰتِ لَعَلَّكُمْ تَعْقِلُونَ
There is not upon the blind [any] constraint nor upon the lame constraint nor upon the ill constraint nor upon yourselves when you eat from your [own] houses or the houses of your fathers or the houses of your mothers or the houses of your brothers or the houses of your sisters or the houses of your father's brothers or the houses of your father's sisters or the houses of your mother's brothers or the houses of your mother's sisters or [from houses] whose keys you possess or [from the house] of your friend. There is no blame upon you whether you eat together or separately. But when you enter houses, give greetings of peace upon each other – a greeting from Allah, blessed and good. Thus does Allah make clear to you the verses [of ordinance] that you may understand.
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ لِيَسْتَـْٔذِنكُمُ ٱلَّذِينَ مَلَكَتْ أَيْمَٰنُكُمْ وَٱلَّذِينَ لَمْ يَبْلُغُوا۟ ٱلْحُلُمَ مِنكُمْ ثَلَٰثَ مَرَّٰتٍۢ ۚ مِّن قَبْلِ صَلَوٰةِ ٱلْفَجْرِ وَحِينَ تَضَعُونَ ثِيَابَكُم مِّنَ ٱلظَّهِيرَةِ وَمِنۢ بَعْدِ صَلَوٰةِ ٱلْعِشَآءِ ۚ ثَلَٰثُ عَوْرَٰتٍۢ لَّكُمْ ۚ لَيْسَ عَلَيْكُمْ وَلَا عَلَيْهِمْ جُنَاحٌۢ بَعْدَهُنَّ ۚ طَوَّٰفُونَ عَلَيْكُم بَعْضُكُمْ عَلَىٰ بَعْضٍۢ ۚ كَذَٰلِكَ يُبَيِّنُ ٱللَّهُ لَكُمُ ٱلْءَايَٰتِ ۗ وَٱللَّهُ عَلِيمٌ حَكِيمٌۭ
O you who have believed, let those whom your right hands possess and those who have not [yet] reached puberty among you ask permission of you [before entering] at three times: before the dawn prayer and when you put aside your clothing [for rest] at noon and after the night prayer. [These are] three times of privacy for you. There is no blame upon you nor upon them beyond these [periods], for they continually circulate among you – some of you, among others. Thus does Allah make clear to you the verses; and Allah is Knowing and Wise.
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ لَا يَسْخَرْ قَوْمٌۭ مِّن قَوْمٍ عَسَىٰٓ أَن يَكُونُوا۟ خَيْرًۭا مِّنْهُمْ وَلَا نِسَآءٌۭ مِّن نِّسَآءٍ عَسَىٰٓ أَن يَكُنَّ خَيْرًۭا مِّنْهُنَّ ۖ وَلَا تَلْمِزُوٓا۟ أَنفُسَكُمْ وَلَا تَنَابَزُوا۟ بِٱلْأَلْقَٰبِ ۖ بِئْسَ ٱلِٱسْمُ ٱلْفُسُوقُ بَعْدَ ٱلْإِيمَٰنِ ۚ وَمَن لَّمْ يَتُبْ فَأُو۟لَٰٓئِكَ هُمُ ٱلظَّٰلِمُونَ
O you who have believed, let not a people ridicule [another] people; perhaps they may be better than them; nor let women ridicule [other] women; perhaps they may be better than them. And do not insult one another and do not call each other by [offensive] nicknames. Wretched is the name of disobedience after [one's] faith. And whoever does not repent – then it is those who are the wrongdoers.
يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوا۟ ٱجْتَنِبُوا۟ كَثِيرًۭا مِّنَ ٱلظَّنِّ إِنَّ بَعْضَ ٱلظَّنِّ إِثْمٌۭ ۖ وَلَا تَجَسَّسُوا۟ وَلَا يَغْتَب بَّعْضُكُم بَعْضًا ۚ أَيُحِبُّ أَحَدُكُمْ أَن يَأْكُلَ لَحْمَ أَخِيهِ مَيْتًۭا فَكَرِهْتُمُوهُ ۚ وَٱتَّقُوا۟ ٱللَّهَ ۚ إِنَّ ٱللَّهَ تَوَّابٌۭ رَّحِيمٌۭ
O you who have believed, avoid much [negative] assumption. Indeed, some assumption is sin. And do not spy or backbite each other. Would one of you like to eat the flesh of his brother when dead? You would detest it. And fear Allah; indeed, Allah is Accepting of repentance and Merciful.
يَٰٓأَيُّهَا ٱلنَّاسُ إِنَّا خَلَقْنَٰكُم مِّن ذَكَرٍۢ وَأُنثَىٰ وَجَعَلْنَٰكُمْ شُعُوبًۭا وَقَبَآئِلَ لِتَعَارَفُوٓا۟ ۚ إِنَّ أَكْرَمَكُمْ عِندَ ٱللَّهِ أَتْقَىٰكُمْ ۚ إِنَّ ٱللَّهَ عَلِيمٌ خَبِيرٌۭ
O mankind, indeed We have created you from male and female and made you peoples and tribes that you may know one another. Indeed, the most noble of you in the sight of Allah is the most righteous of you. Indeed, Allah is Knowing and Acquainted.
وَقُل لِّعِبَادِى يَقُولُوا۟ ٱلَّتِى هِىَ أَحْسَنُ ۚ إِنَّ ٱلشَّيْطَٰنَ يَنزَغُ بَيْنَهُمْ ۚ إِنَّ ٱلشَّيْطَٰنَ كَانَ لِلْإِنسَٰنِ عَدُوًّۭا مُّبِينًۭا
And tell My servants to say that which is best. Indeed, Satan induces [dissension] among them. Indeed Satan is ever, to mankind, a clear enemy.
From the hadith
مَنْ كَانَ يُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ فَلْيَقُلْ خَيْرًا أَوْ لِيَصْمُتْ وَمَنْ كَانَ يُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ فَلْيُكْرِمْ جَارَهُ وَمَنْ كَانَ يُؤْمِنُ بِاللَّهِ وَالْيَوْمِ الآخِرِ فَلْيُكْرِمْ ضَيْفَهُ
It is reported on the authority of Abu Huraira that the Messenger of Allah (ﷺ) observed:He who believes in Allah and the Last Day should either utter good words or better keep silence; and he who believes in Allah and the Last Day should treat his neighbour with kindness and he who believes in Allah and the Last Day should show hospitality to his guest
Quran verses use the Arabic text with the Sahih International translation. Hadith are from Sahih al-Bukhari and Sahih Muslim. A translation is not the Quran itself, and one text does not give a full ruling. Open each link and read the text in its full context.