Ruling on men selling underwear to women

Firstly: 

There is nothing wrong with opening a shop to sell women’s
underwear, so long as one pays attention to Islamic rulings. So he should
not sell anything but that which it is permissible for him to sell, which
does not contain anything prohibited, like crosses, and he should not
display these clothes on models in a way that may provoke desire or is
contrary to modesty. 

Please see the answer to question no.
178107. 

Secondly: 

With regard to men working in such shops, in principle it is
permissible for a man to deal with a non-mahram woman, buying and selling,
renting, and so on, so long as the seller adheres to Islamic guidelines. 

One of the matters to which attention should be paid with
regard to selling these kinds of garments is to differentiate between two
business formats: 

1.

Large stores in which the goods are displayed and already
priced, and the woman picks up whatever she wants, and the role of the
seller is limited to working out what the customer owes only. There is
nothing wrong with this format. 

2.

Small stores in which the woman needs to speak with the
worker and ask about the characteristics of various products, and the seller
needs to present the product attractively and promote it, so the seller of
women’s underwear may indulge in talking in a way that causes embarrassment
or there is the fear of temptation, especially nowadays when dignity is
lacking and many women have little modesty. 

Such work is not befitting for the pious Muslim who is keen
to adhere to his religion, and he should avoid it, because of what is
narrated of hadiths that warn against the temptation of women. That is
supported by real-life stories of temptation experienced by many of those
who work in such shops. 

According to a hadith the authenticity of which is agreed
upon, the Prophet (blessings and peace of Allah be upon him) said: “I have
not left behind me among the people any fitnah (trial) that is more harmful
to men than women.” And he (blessings and peace of Allah be upon him) said:
“Beware of this world and beware of women, for the first fitnah (trial)
among the Children of Israel had to do with women.” Narrated by Muslim
(2742) 

So selling women’s underwear should either be done in large
stores, as described in the first example, or it should be done in stores
that are exclusively for women, in which women are in charge of selling
things that are only for women. 

And Allah knows best.