- Peninei Halakha
The fifth way in which we afflict ourselves on Tisha Be-Av is by abstaining from sexual relations. In order to distance ourselves from transgressing this prohibition, a couple must behave on the night of Tisha Be-Av as they do when the woman is a nida. That is, they may not touch each other, sleep in the same bed, or pass things to each other from hand to hand. During the day, they do not need to observe all the precautionary measures that apply while the woman is a nida, but they still may not touch each other affectionately or sleep in the same bed.12
12 554:18. Two adjacent beds are considered one bed. The Aĥaronim write that one should be stringent on Tisha Be-Av with regard to all the precautionary measures that couples observe during the nida period, just as one does on Yom Kippur ( 615:1). According to most poskim, one should be stringent both on the day and night of Yom Kippur. Taz maintains that one does not need to be stringent during the day of Yom Kippur. Regarding Tisha Be-Av, however, many poskim write that one does not need to observe the precautions during the day, since everyone is mourning and the women do not adorn themselves; therefore, there is no reason to be concerned that contact between husband and wife will lead to sexual intercourse ( 554:37, Kaf Ha-ĥayim 554:85). Some rule stringently with regard to touching even during the day (Kitzur 124:12, Hilkhot Ĥagim 26:49). Either way, it seems that everyone agrees that affectionate touching is prohibited even during the day, as is sleeping in the same bed.