Yevamot 61b:15יבמות ס״א ב:ט״ו
MISHNA: A man may not neglect the mitzva to be fruitful and multiply unless he already has children. Beit Shammai say: One fulfills this mitzva with two males, and Beit Hillel say: A male and a female, as it is stated: “Male and female He created them” (Genesis 5:2).
Yevamot 61b:16יבמות ס״א ב:ט״ז
GEMARA: The Gemara infers from the mishna’s wording that if he already has children he may neglect the mitzva to be fruitful and multiply, but he may not neglect the mitzva to have a wife. This supports what Rav Naḥman said in the name of Shmuel, who said: Even if a man has several children, it is prohibited to remain without a wife, as it is stated: “It is not good that the man should be alone” (Genesis 2:18).
Mishneh Torah, Marriage 15:16משנה תורה, הלכות אישות ט״ו:ט״ז
Although a man has fulfilled the mitzvah of being fruitful and multiplying, he is bound by a Rabbinic commandment not to refrain from being fruitful and multiplying as long as he is physically potent. For anyone who adds a soul to the Jewish people is considered as if he built an entire world.
Similarly, it is a mitzvah of our Sages that a man should not live without a wife, so that he will not be prompted to [sexual] thoughts. Similarly, a woman should not live without a man, so that she will not be suspected [of immoral conduct].
Similarly, it is a mitzvah of our Sages that a man should not live without a wife, so that he will not be prompted to [sexual] thoughts. Similarly, a woman should not live without a man, so that she will not be suspected [of immoral conduct].
Shulchan Arukh, Even HaEzer 1:8שולחן ערוך, אבן העזר א׳:ח׳
Even though he fulfilled the obligation of be fruitful and multiply, he is forbidden from being without a wife and he needs to marry a woman who is capable of bearing children (see Yevamot 61b). He may sell a sefer Torah in order to do so if he has a doubt that he has enough children or if he has a doubt that he has married a women of child bearing capability. If he does not have children he sells so that he can marry a woman capable of bearing children but if he has children he should not sell it and marry a woman who is capable of bearing children, but he should not be without a wife. And some say, that even if he has sons, he sells the sefer Torah to marry a woman capable of bearing children. Isserless: However, if it is recognized that the will not be more grandchildren and it is not appropriate that more will not be born to him, he marries a women who is not capable of bearing children, and thus if he has many sons and he fears that if he marries a woman of child bearing age an altercation will come and discord will come between the children and his wife he is permitted to marry a woman who is not capable of bearing children but it is forbidden to settle down without a wife because of this fear.
Arukh HaShulchan, Even HaEzer 1:7ערוך השולחן, אבן העזר א׳:ז׳
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Arukh HaShulchan, Even HaEzer 1:8ערוך השולחן, אבן העזר א׳:ח׳
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