'A seed' signifies the ultimate and primary levels in a person. It also signifies good and truth from the Lord. In an opposite sense, it signifies falsity of doctrine and hellish falsity. 'A seed' signifies everyone who constitutes the Lord's spiritual kingdom and faith grounded in charity.

In Genesis 12:7, 8:15, 16, 'a seed' signifies love and everyone who has love.

(References: Arcana Coelestia 1025)

A 'void', or 'Vacuity' denotes a person's state before regeneration. From Arcana Coelestia 7: "The first state is the state which precedes, both the state existing from earliest childhood onwards and that existing immediately before regeneration; and it is called a void, emptiness, and thick darkness.

In Genesis 1:2, this signifies lacking good, as with man's state before regeneration. (Arcana Coelestia 17)

In Psalm 89:39, this signifies that the Jewish nation had destroyed its conjunction with the Lord and the church. (The Inner Meaning of the Prophets and Psalms 339)