'The spirit of God,' as in Genesis 1:2, signifies the divine mercy of the Lord.

'The spirit of God' denotes good from an interior level, so from the divine. The spirit of God is what proceeds from the divine, so from good itself, because the divine is good itself, and what proceeds from it is truth within which is good. This is what 'the spirit of God' signifies in the Word, because the spirit itself does not proceed, but the truth itself within which is good, the spirit being the instrument which produces it.

(References: Arcana Coelestia 19; Divine Love and Wisdom 100)

The firmament of heaven represents mutual love. The firmament, as in Genesis 1, signifies the internal man.

(References: Arcana Coelestia 24)