Is it permissible for my husband to speak on the phone with the wife of his deceased friend to check on her and her son, knowing that she communicates with him religiously via email, and that my husband does not believe the verse: "Then do not be soft in speech, lest he in whose heart is disease should covet" applies to her?

It is permissible for a man to speak with a non-mahram woman (a woman who is not a close relative) out of necessity, provided that Islamic guidelines are observed, such as avoiding private seclusion (khulwa) and not softening the speech. A woman's voice is not considered 'awrah (something that must be covered or concealed), and the forbidden softening of speech refers to making the voice tender and alluring. Conversation with a young non-mahram woman is often not safe, which is why some scholars prohibited offering condolences to a young woman. One must be careful when conversing with her unless there is a legitimate necessity. She, in turn, must fear Allah and refrain from conversing with them without a legitimate necessity. Allah Almighty says: "O you who have believed, do not follow the footsteps of Satan. And whoever follows the footsteps of Satan - then indeed, he enjoins immorality and wrongdoing. And if not for the favor of Allah upon you and His mercy, not one of you would have been pure ever, but Allah purifies whom He wills, and Allah is Hearing and Knowing." (An-Nur: 21). They should be advised with wisdom and good admonition.