Now it behooves us to see that it is Binah, and it is called Tevunah. Why is it called Tevunah rather than Binah? He answers, Ima is called Tevunah when she suckles the two children, the son and the daughter that are called Vav-Hei; they are Zeir Anpin and Malchut. At that time, it is called Tevunah, because everything is included in the letters spelling it: ben (son), bat (daughter) Vav-Hei; since the spelling of Tevunah contains ben, bat and Vav-Hei. It is one wholeness, namely, Tevunah.
In the book of Rav Hamnuna Saba he said, the first composition King Solomon revealed, “Behold, you are fair, my love” (Song of Songs 1:14) was about that, that is, it refers to Ima, whom Aba called beloved. The second composition, “Come with me from Lebanon, my bride” (Ibid. 4:8) is called a bride, who is the lower female, namely, Malchut. Some say both refer to the lower female, Malchut; this is not the case. The first Hei of Yud Hei Vav Hei is not called a bride but beloved, as Aba and Ima are called beloved; and the last Hei is called a bride at certain time. There are many times when the male, Zeir Anpin, does not unite with her but leaves her. Of that time, it is written “Also you shall not approach to a woman in the impurity of her menstrual flow” (Vayikra 18:19). When the female is purified and the male wishes to unite with her, she is called a bride; she comes verily like a bride. That is, Malchut is rebuilt anew with ten Sfirot for every union and is considered a bride. The union of Aba and Ima, however, is continuous and never ceases as shall be explained.