Al-Ahzab · 33:53

53. O those who have faith in Allah and do whatever Allah has legislated for them! Do not enter the houses of the Prophet except after he has given you permission to enter by inviting you for food. And do not come too early so you end up sitting for longer than needed, waiting for the food to be cooked, rather when you are invited, then enter and after you have eaten, return. Do not remain behind socialising with each other, because remaining behind causes inconvenience to the Prophet (peace be upon him) and he feels embarrassed to ask you to leave, but Allah is not embarrassed to command you to do what is right, and so he has commanded you leave so that you do not cause inconvenience to him (peace be upon him) by staying for too long. And when you ask for something from the wives of the Prophet (peace be upon him) i.e. utensils etc. then ask from behind a veil, not face to face, in a manner that you cannot see them with your eyes. This is to protect them due to the stature of the Messenger of Allah. Asking from behind a veil is purer for your hearts and their hearts, so that Satan cannot influence your hearts through whispers and beautifying evil. And O believers! It is not befitting for you to cause inconvenience to the Messenger of Allah by remaining behind to socialise, nor that you marry his wives after he has passed away, because they are the wives of the believers and it is not permissible for anyone to marry his mother. Indeed, that causing inconvenience - of which is your marrying his wives after his death - is forbidden and regarded as a great sin by Allah.