Reference: Fataawa Mu’aasirah – Page 81
al-Mowsoo’ah – 4807
Questioner: Is it permissible for the husband and wife to talk about sex over the telephone [and by doing so] they arouse each other until one of them or both of them have an orgasm [making sure not to use the hand because it is haraam]. We do this because my husband travels alot and we only [get to] see each other every four months?
Shaykh: There is no harm [in this]. Yes this is permissible.
Questioner: And [is this permissible] even with the use of the hand?
Shaykh: There is some [element of] uncertainty in [the issue of] using the hand; And it is not permissible except if he fears falling into adultery.
Questioner: [So] there is no harm [in doing so] without using the hand?
Shaykh: Yes, there is no harm [in doing so] without using the hand [while] he imagines he is with her. And it is befitting upon them both that they are careful no-one listens to their speech or spies upon them. And Allaah [alone] has the Complete knowledge [of all affairs].