Is it a wife's duty to have sex after marriage? If yes, could you please quote which Hindu scripture says so?
Is a wife duty bound to do sex after marriage?
Yes, both husband and wife are required to have sex in marriage after every menstrual period.
Verses from various Dharma Shastras:
Manusmriti 3.45 - One should observe the rule of approaching (one’s wife) during the period of her season,—ever attached to his own wife. In consideration of her he may approach her with a desire for sexual intercourse, except on the sacred days.
Gautama (5.1-2).—‘He shall approach her during the season; or on all days except those that have been prohibited.’
Āpastamba-Dharmasūtra (2.1.15, 18).—‘By approaching his wife during the seasons, one maintains one’s vows; even during the intervening days, ho should approach only his wife.’
Vaśiṣṭha (12.18).—‘He should have intercourse only with his wife, during her seasons, except the forbidden days.’
Viṣṇu (69.1).—‘He shall not approach his wife on the eighth, fourteenth and fifteenth days of the fortnight.’
Yājñavalkya (1.79-81).—‘Sixteen are the nights of season for women; during this season, he shall lie with her on the even nights, avoiding the first four nights; acting thus, he would be as good as a Religious Student. In approaching his wife, he shall avoid the asterisms of Maghā and Mūla. Or, he may approach her according to his desire, always bearing in mind what is good for women; he should ever remain devoted to his own wife.’
Pāraskara Gṛhyasūtra (1.11.7-8).—‘Having married her, he should go to her during her seasons; or whenever they desire.’
Hārīta (Vīramitrodaya-Āhnika, p. 559).—‘After she has bathed on the fourth day, he shall approach her on the even nights.’
Ātharvaṇa Śruti (Parāśaramādhava, p. 497).—‘Those who have recourse to sexual intercourse during the day, pour out their life-breath; if one has intercourse during the night, it is as good as celibacy.’
Śaṅkha-Likhita (Parāśaramādhava, p. 497).—‘Even during the period, one shall not have intercourse during the day.’
Devala (Parāśaramādhava, p. 498).—‘If a man, when healthy, does not approach his wife during the period, he incurs the sin of killing the embryo.’
Bṛhaspati (Parāśaramādhava, p. 499).—‘Excess of woman’s seed makes the progeny female, excess of man’s seed makes the progeny male; therefore for increasing his seed, the man shall eat oily and delicious food.’
It is a sin to not approach one's wife:
Manusmriti 9.4 - Censurable is the father who gives her not away at the right time; censurable the husband who approaches her not; and censurable the son who, on the death of her husband, does not take care of her.
Baudhāyana (Parāśaramādhava, p. 498).—‘If a man approaches not his wife during the period, for three years, he incurs the sin of killing the embryo. He who approaches not his wife during the period, and who approaches her apart from the period, the sin of both is equal, as also that of the man who throws out his semen unnaturally.’
However, the wife must also be willing:
Rules for Sexual Activity, Vishnu Purāṇa 3.11:
- In proper time, under the influence of an auspicious planet and in an auspicious moment or on even nights (tithis) one should have sex with his own wife.
112 – 113. One should not approach a woman who is unbathed, sick, menstruating, unwilling, angry, un-recommended, pregnant, unskilled (adaksinam), in love with another (anya-kamam), lacking in libido (akamam) nor committed to another (anya-yoshitam), nor if she is hungry or over-fed. He too should also be free from all these imperfections.
Yes, wife has to go by husband's desires and not the vice-versa.
Verily, of created things here earth is the essence; of earth, water; of water, plants; of plants, flowers; of flowers, fruits; of fruits, man (purusa); of man, semen.
Prajâpati ('Lord of creatures') bethought himself: 'Come, let me provide him a firm basis!' So he created woman. When he had created her, he revered her below.--Therefore one should revere woman below.--He stretched out for himself that stone which projects. With that he impregnated her.
Her lap is a sacrificial altar; her hairs, the sacrificial grass; her skin, the soma-press. The two labia of the vulva are the fire in the middle. Verily, indeed, as great as is the world of him who sacrifices with the Vâjapeya ('Strength-libation') sacrifice, so great is the world of him who practises sexual intercourse, knowing this; he turns the good deeds of women to himself. But he who practises sexual intercourse without knowing this-women turn his good deeds unto themselves.
This, verily, indeed, it was that Uddâlaka Âruṅi knew when he said:--
This, verily, indeed, it was that Nâka Maudgalya knew when he said:--
This, verily, indeed, it was that Kumârahârita knew when he said: 'Many mortal men, Brahmans by descent, go forth from this world, impotent and devoid of merit, namely those who practise sexual intercourse without knowing this.'
[If] even this much 1 semen is spilled, whether of one asleep or of one awake,  then he should touch it, or [without touching] repeat:--
'What semen has of mine to earth been spilt now, Whate'er to herb has flowed, whate'er to water--
This very semen I reclaim! Again to me let vigor come! Again, my strength; again, my glow! Again the altars and the fire Be found in their accustomed place!'
Having spoken thus, he should take it with ring-finger and thumb, and rub it on between his breasts or his eye-brows.
- Now, if one should see himself in water, he should recite over it the formula: 'In me be vigor, power, beauty, wealth, merit!'
This, verily, indeed, is loveliness among women: when she has removed the clothes of her impurity. Therefore when she has removed the clothes of her impurity and is beautiful, one should approach and invite her.
If she should not grant him his desire, he should bribe her. If she still does not grant him his desire, he should hit her with a stick or with his hand, and overcome her, saying: 'With power, with glory I take away your glory!' Thus she becomes inglorious.
If she should yield to him, he says: 'With power, with glory I give you glory!' Thus they two become glorious.
The woman whom one may desire with the thought, 'May she enjoy love with me!'--after inserting the member in her, joining mouth with mouth, and stroking her lap, he should mutter:--
'Thou that from every limb art come, That from the heart art generate, Thou art the essence of the limbs! Distract this woman here in me, As if by poisoned arrow pierced!'
Now, the woman whom one may desire with the thought, 'May she not conceive offspring!'--after inserting the member in her and joining mouth with mouth, he should first inhale, then exhale, and say: 'With power, with semen, I reclaim the semen from you!' Thus she comes to be without seed.
Now, the woman whom one may desire with the thought, 'May she conceive!'--after inserting the member in her and joining mouth with mouth, he should first exhale, then inhale, and say: 'With power, with semen, I deposit semen in you!' Thus she becomes pregnant.
Now, if one's wife have a paramour, and he hate him, let him put fire in an unannealed vessel, spread out a row of reed arrows in inverse order, and therein sacrifice in inverse order those reed arrows, their heads smeared with ghee, saying:--
'You have made a libation in my fire! I take away your in-breath and out-breath (prâṅâpânau)--you, so-and-so!
You have made a libation in my fire! I take away your sons and cattle 1--you, so-and-so!
You have made a libation in my fire! I take away your sacrifices and meritorious deeds 1--you, so-and-so!
You have made a libation in my fire! I take away your hope and expectation 1--you, so-and-so!'
Verily, he whom a Brahman who knows this curses--he departs from this world impotent and devoid of merit. Therefore one should not desire dalliance with the spouse of a person learned in sacred lore (s'rotriya) who knows this, for indeed he who knows this becomes superior. 2
- Now, when the monthly sickness comes upon anyone's wife, for three days she should not drink from a metal cup, nor put on fresh clothes. > Neither a low-caste man nor a low-caste woman nor her husband should touch her. At the end of the three nights she should bathe and should have rice threshed.