(From Wiki)
The traditional viewpoint is that the Torah mentions homosexuality twice in the book of Leviticus (JPS):
וְאֶת-זָכָר—לֹא תִשְׁכַּב, מִשְׁכְּבֵי אִשָּׁה: תּוֹעֵבָה, הִוא.
Lev.18:22 "Thou shalt not lie with mankind, as with womankind; it is abomination."
וְאִישׁ, אֲשֶׁר יִשְׁכַּב אֶת-זָכָר מִשְׁכְּבֵי אִשָּׁה—תּוֹעֵבָה עָשׂוּ, שְׁנֵיהֶם; מוֹת יוּמָתוּ, דְּמֵיהֶם בָּם.
Lev.20:13 "And if a man lie with mankind, as with womankind, both of them have committed abomination: they shall surely be put to death; their blood shall be upon them."
Lesbian sexual activity
Although there is no direct textual prohibition of homosexual acts between women (lesbianism) anywhere in the Torah, such behavior is widely viewed as unacceptable by most rabbis. It is based on a Drash interpretation of the Biblical verse "Do not follow the ways of Egypt where you once lived, nor of Canaan, where I will be bringing you. Do not follow any of their customs." (Leviticus 18:3).
A midrash, Sifra Aharei Mot 8:8–9, states that this refers to sexual customs, and that one of those customs was the marriage of women to each other, as well as a man to a woman and to her daughter. Maimonides, in his Mishneh Torah, summarizes the matter as follows:[1]
For women to be mesollelot with one another is forbidden, as this is the practice of Egypt, which we were warned against: "Like the practice of the land of Egypt . . . you shall not do" (Leviticus 18:3). The Sages said [in the midrash of Sifra Aharei Mot 8:8–9], "What did they do? A man married a man, and a woman married a woman, and a woman married two men." Even though this practice is forbidden, one is not lashed [as for a Torah prohibition] on account of it, since there is no specific prohibition against it, and there is no real intercourse. Therefore, [one who does this] is not forbidden to the priesthood because of harlotry, and a woman is not prohibited to her husband by this, since it is not harlotry. But it is appropriate to administer to them lashings of rebellion [i.e., those given for violation of rabbinic prohibitions], since they did something forbidden. And a man should be strict with his wife in this matter, and should prevent women known to do this from coming to her or from her going to them.
"Rabbi Huna said in the name of Rabbi Joseph, 'The generation of the Flood was not wiped out until they wrote marriage documents for the union of a man to a male or to an animal.'"[2]
Another important reference is found in the Babylonian Talmud:
"'Ula said: Non-Jews [litt. Bnei Noach, the progeny of Noah] accepted upon themselves thirty mitzvot [divinely ordered laws] but they only abide by three of them: the first one is that they do not write marriage documents for male couples, the second one is that they don't sell dead [human] meat by the pound in stores and the third one is that they respect the Torah.'" [3]