Reference for Yevamot 122:18

בית שמאי אומרים שני זכרים: מאי טעמייהו דבית שמאי ילפינן ממשה דכתיב (דברי הימים א כג, טו) בני משה גרשום ואליעזר ובית הלל ילפינן מברייתו של עולם ובית שמאי לילפי מברייתו של עולם אין דנין אפשר

This provides support for a statement R. Nahman made in the name of Samuel who ruled that although a man may have many children he must not remain without a wife, for it is said in the Scriptures, It is not good that the man should be alone.<span class="x" onmousemove="('comment',' Gen. II, 18. ');">⁴⁷</span> Others read: [This<span class="x" onmousemove="('comment',' [Since the Mishnah does not state, A man shall not marry a woman who is incapable of bearing children unless he already has children (Tosaf.)]. ');">⁴⁸</span> implies] if he has children he may abstain from performing the duty of propagation and also from that of living with a wife. May it, then, be said that this presents an objection against the statement R. Nahman made in the name of Samuel?<span class="x" onmousemove="('comment',' Supra, that a man must never remain unmarried. ');">⁴⁹</span> — No; if he has no children he must marry a woman capable of procreation; and if he has children he may marry a woman who is incapable of procreation. What is the practical difference?<span class="x" onmousemove="('comment',' As regards the duty of marriage. In either case one must not remain single. ');">⁵⁰</span> — In respect of selling a Scroll of the Law for the sake of children.<span class="x" onmousemove="('comment',' Only a man who has no children must sell even such a precious object if thereby he is enabled to marry a woman capable of procreation. If he has children such a sale is forbidden, and he must contract a less expensive marriage with an old or sterile woman. ');">⁵¹</span> BETH SHAMMAI RULED: TWO MALES. What is Beth Shammai's reason? We make an inference from Moses, in connection with whom it is written, The sons of Moses: Gershom and Eliezer.<span class="x" onmousemove="('comment',' I Chron. XXIII, 15. ');">⁵²</span> And Beth Hillel? — We infer from the creation of the world. Let Beth Shammai also infer from the creation of the world! — The possible cannot be inferred

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