It is for this purpose that Imma enters into Zeir Anpin... i.e. as mentioned above, Imma becomes “bone of his bones...” (through giving him her Netzach-Hod-Yesod)....and makes brotherly love reign among his Sefirot. This is the bond in which Imma binds together the different parts of Zeir Anpin with flashing excitement and joy.
This is done through Malchut... The underlying principle here is that “Whoever remains without a wife remains without joy” (Yevamot 62b). This is also the mystery of Shabbat. The greatness of the Shechinah – the female aspect – lies in bringing completion to the male. The underlying principle is that Imma does not rest upon Zeir Anpin except when the Nukva is with him, as is clear from many passages in the Zohar and Tikkuney Zohar. This is explained by the fact that the Nukva is the root of the recipients, and when the lights wish to shine blessing on their recipients, everything is full of joy and radiant excitement – “God will rejoice in His works” (Psalms 104:31). However, this depends on the deeds of those in the lower realms. When the lower realms are ready, it means that the Nukva, which is their root, is prepared and ready to be filled (becoming a receiving vessel). The lights then flash with great power and joy, and all the gates are opened. Tzaddik, the active influence, is then blessed from Imma above and becomes filled with all good. However, if the lower realms are not prepared, God forbid, it means that their root – the Nukva – is not ready to receive. Of this it is said, “It grieved Him in His heart” (Genesis 6:6). All the lights are then occluded, and this is the mystery of, “The waters are gone from the sea (=Nukva) and the river (=Zeir Anpin) is parched and dried up” (Job 14:11), as explained in various places.