creating it in the image of God—
creating them male and female. (28) God blessed them and God said to them, “Be fertile and increase, fill the earth and master it; and rule the fish of the sea, the birds of the sky, and all the living things that creep on earth.”
And God saw all that God had made, and found it very good. And there was evening and there was morning, the sixth day.
תני רב יוסף שארה זו קרוב בשר שלא ינהג בה מנהג פרסיים שמשמשין מטותיהן בלבושיהן מסייע ליה לרב הונא דאמר רב הונא האומר אי אפשי אלא אני בבגדי והיא בבגדה יוציא ונותן כתובה:
Rav Yosef taught There must be close bodily contact during sex, unlike the custom of the Persians who perform their marital duties in clothes. This supports the ruling of Rav Huna. As Rav Huna said: A husband who says, "I will not perform [my marital duties] unless I wear my clothes and she wears hers, must [divorce her] and give her the ketubah [settlement].
When a man has taken a bride, he shall not go out with the army or be assigned to it for any purpose; he shall be exempt one year for the sake of his household, to give happiness to the woman he has married.
"to give happiness" - sex not for purpose of procreation but rather for pleasure.
(ו) התלמידים יוצאין לתלמוד תורה שלא ברשות. שלשים יום. הפועלים שבת אחת. העונה האמורה בתורה. הטיילין בכל יום. הפועלים שתים בשבת. החמרים אחת בשבת. הגמלים. אחת לשלשים יום. הספנים אחת לששה חדשים. דברי רבי אליעזר:
Students who leave for the purpose of studying Torah without the consent of their wives [have] thirty days; laborers, one week. [The law of providing sexual] pleasure [to one's wife] that is stated in the Torah [is as follows]: one at leisure, daily; laborers, twice a week; donkey drivers, once a week; camel drivers, once every thirty days; navigators every six months; these are the words of Rabbi Eliezer.
(יד) תַּשְׁמִישׁ הַמִּטָּה מֵעֹנֶג שַׁבָּת הוּא. לְפִיכָךְ עוֹנַת תַּלְמִידֵי חֲכָמִים הַבְּרִיאִים מְשַׁמְּשִׁין מִלֵּילֵי שַׁבָּת לְלֵילֵי שַׁבָּת.
Sexual relations are considered a dimension of Shabbat pleasure. Therefore Torah scholars fulfill their marital obligations once a week, on the Shabbat.
Here is how Rashi explains it: “When your husband caresses you to arouse your desire for intercourse and holds the breasts with one hand and “that place” with the other give the breasts [at first] to increase his passion and do not give him the place of intercourse too soon until his passion increases and he is in pain with desire.”
