To be fruitful relates to goodnesses, and to be multiplied, truths.

(References: Arcana Coelestia 1014, 1018)

'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)