12. Marital relations are forbidden [on Tish'ah B'av] (1) . It is proper
to be stringent and refrain even from touching one's wife (2).
(1) There are 5 forms of physical deprivation ("Inuyim") that we are
obligated to undergo on Tish'ah B'av: not eating or drinking, not bathing,
not anointing, not wearing leather shoes and not engaging in marital
relations. The same five activities are Biblically prohibited on Yom Kippur.
(2) All the restrictions on physical contact between a husband and wife
that apply when the wife is in "niddah" (menstruating), also apply on Yom
Kippur, because marital relations are Biblically prohibited (See Shulchan
Aruch 615:1). Therefore, on Yom Kippur, one may not touch one's wife for
the entire night and day, as a safeguard against being drawn into marital
relations. There are those who say that the same rules apply to Tish'ah
B'av, during which marital relations are rabbinically forbidden. However,
since there are those who say that the prohibition against touching one's
wife doesn't apply on Tish'ah B'av, and since women do not go out of their
way to dress attractively on Tish'ah B'av (as they would on Yom Kippur),
the prevailing practice is to be lenient and permit touching one's wife
during the day on Tish'ah B'av (Mishan Berura 554:37 and Sha'ar Ha'Tziyun
554:44). On Tish'ah B'av night, however, it is forbidden to touch one's
wife, and to sleep in the same bed (See Shulchan Aruch 554:18).