Rashi on Genesis 32/רש"י על בראשית ל״ב

1עזים מאתים ותישים עשרים TWO HUNDRED SHE GOATS AND TWENTY HE GOATS — Two hundred she goats have need of twenty he goats, and so too in the case of all the various species the males were in number according to the need of the females. In Genesis Rabbah 76:7 an inference is made from here as regards the minimum period imperative for the marital duty imposed by the Torah - [for] the men of leisure, every day; [for] the laborers, twice a week; [for] the donkey drivers, once a week; [for] the camel drivers, once in thirty days, [for] the sailors, once in six months. I am unable however to show exactly how this inference is arrived at. But it appears to me that we may learn from here at least that this period is not the same for every person, but that it depends upon the amount of labor imposed upon him by his occupation. As we have found here that ten she goats were given to each he goat, and so [too] to each ram; [as] since they are free from work, their way is to be frequently involved in sexual relations and to impregnate ten females - and once an animal becomes pregnant, it does not accept a male. And [concerning] the bulls that engage in work, it only gave four females to the male; and to the donkey who goes on long journeys, [it gave] two females to the male; and to the camels that go on [even] longer journeys, [it gave] one female to the male.