Aslam

Praise be to Allah.

Firstly:

It is permissible for a man to speak to a non-mahram woman if

there is a need to do so, and there is no soft speech on the part of the

woman or enjoyment on the part of the man, and the talk is of something that

is permissible.

But they should limit it to what is necessary, so as to block

the means that may lead to evil, because getting carried away in talking

unnecessarily may lead to something haraam.

Based on that, there is nothing wrong with a man talking to a

woman when buying, selling, asking a question, medical treatment, and so on,

if attention is paid to these guidelines.

For more information, see the answer to question number

1121.

With regard to your husband speaking to that woman and

advising her to keep away from his friend, in this case -- in addition to

the above -- he should weigh up the pros and cons. There may be some

interest to be served in his contacting her, or there may be some negative

outcome, and there may be no need to do that. He could instead send an

anonymous letter in which there is advice, reminders and warnings. This

varies according to the situation of your husband and the situation of the

woman mentioned.

The safest approach is that he not contact her directly,

which may lead him to negative consequences, especially if the woman does

not care about forming relationships with men and nothing will deter her

from that.

Your husband should advise his friend to keep away from that

woman and remind him to fear Allah, may He be exalted.

And Allah knows best.