Passover: "The Fourth Cup...I will take you as my people"

If the first three cups of the Passover Seder are filled and drunk, the fourth cup then, and only then, may be filled.  The lifting of that fourth cup acknowledges the purpose of God to have a people of his own possession.  The drinking of it ratifies, confirms, and agrees to the covenant of "taking."  It is mutual and reciprocal.  It is a covenant freely entered into;  it is the covenant of relationship that joined Boaz and Ruth.  A covenant is not a relationship of superiority/inferiority, but there are necessary pre-conditions:  freedom, deliverance, and redemption.  If any one of these is missing, compromised or deficient, various impediments will be revealed---for example, the people of Israel likely had taken up with the idols of Egypt.  Thus, the necessary freedom, deliverance or redemption are lacking and Israel cannot enter into a true covenant with God.
A covenant is not a contract because contracts are contingent on performance and signify a possible (even likely) inequity and imbalance---usually of power---between the two parties.  Anxiety of one or both parties is resolved by the contract and its terms.  Israel looked at its relationship with God as a contract:  no meat, no land flowing with milk and honey...  God had not performed according to their reading of the contract terms and promises.
Only a free people can come to the fourth cup;  only a delivered people can come to the fourth cup.  Finally, only a people who know their redeemed status can fill, lift, and drink that fourth cup.  By so doing they are "taking" the God of Israel as their own, and the God of Israel is "taking" them.  Such a "taking" has clear connotations of marriage, a union in spirit:  the spirit of the people enters into relationship with the Spirit of God.  And the two become one.  That unity precludes any other possible union with any other spiritual entity or "god."
Such a "taking" cannot be a seduction or raping.  No coercion, no manipulation, no prevailing---neither the most blatant forms nor the most subtle forms---upon the body, soul, or spirit is permissible in a covenantal "taking."  So the relationship of Israel and God is not of a powerful, awesome, and demanding God with a weak, diminutive, and submissive/accommodating Israel...  The fourth cup is drunk fully and willingly and joyfully by both God and Israel.
Relationship is the central characteristic of the Passover journey.  Until there is Freedom, Deliverance, and Redemption, relationship is not possible.  Israel cannot enter into the relationship of Covenant, Israel cannot ratify, confirm or establish that Covenant relationship until the first three cups have been drunk.
So it is relationship, relationship, relationship...
All this must precede the "marriage to the Land."  The prophets describe Israel's dwelling in the set aside or "holy" land as a marriage, which is to further reveal the relationship between the covenant partners.  If the Land is polluted---physically, soulishly, or spiritually---the nature of that dwelling relationship is certainly suspect.  But that is another Cup for another "moed" (appointed time)!