Reference for Bava Batra 239:8
באבות הוא אומר (במדבר לו, ח) וכל בת יורשת נחלה והרבה מצות נצטוו בנים שלא נצטוו אבות הא מפני שיש באבות שאין בבנים ויש בבנים מה שאין באבות הוצרך לומר אבות הוצרך לומר בנים
[namely], that they should he married only to such as are worthy of them.<span class="x" onmousemove="('comment',' This advice they carried out in marrying their uncles' sons. Ibid. II. ');"><sup>28</sup></span> Rabbah raised an objection: 'Say unto them,<span class="x" onmousemove="('comment',' Lev. XXII, 3. ');"><sup>29</sup></span> [means] to those who stood on Mount Sinai; throughout your generations,<span class="x" onmousemove="('comment',' Lev. XXII, 3. ');"><sup>29</sup></span> [refers] to the coming generations. If fathers were mentioned, why were sons [also] mentioned; and if sons were mentioned, why should fathers be mentioned? — Because some [precepts] which apply to the fathers<span class="x" onmousemove="('comment',' Lit., 'which is in the fathers'. ');"><sup>30</sup></span>