מדרש על בראשית 49:31

8) This tells me only of the patriarchs. Whence do I derive (the same for) the matriarchs? From (the triple) eth, eth, eth, "eth" signifying the matriarchs, viz. (Bereshith 49:31), "There they buried Avraham and ('ve'eth') Sarah his wife." And whence is it derived that a covenant has been made with the land? From "and the land will I remember" (as I remember the covenant with the patriarchs.)