(Devarim 32:47) "For it is not an empty thing for you; for it is your life, and by this thing you shall prolong days": There is nothing empty in the Torah, for which, if you fulfill it, you will not be rewarded in this world, with the principal remaining for the world to come. Know this to be so, for they said: Why is it written (Bereshith 36:22) "And the sister of Lotan was Timna," and (Ibid. 36:12) "And Timna was a concubine to Elifaz (the son of Esav)"?
Because she said: "I am not worthy of being his wife; (at least) let me be his concubine." Why all this? To apprise us of the greatness of our father Abraham, kings and sultans [(Timna was a daughter of royalty)] desiring to marry into his family. Now does this not follow a fortiori?
If Esav, who kept only one mitzvah, that of honoring his father — kings and sultans desired to marry into his family, how much more so would they run to do so with Jacob the tzaddik, who fulfilled all of the mitzvoth, viz. (Ibid. 25:27) "And Jacob was a whole man!"