Absolute category statements about God are quite rare. Here are the ones I could find. Their meaning is always the same, that God is placed in the category as stated.
- God is Love, Ὁ Θεὸς ἀγάπη ἐστίν, 1 John 4:8, 16
This states that God is in the category of being whose being is essentially Love. [In this respect, Christians are to imitate God; but that is another question.]
- God is One, Θεὸς εἷς ἐστιν, Gal 3:20, James 2:19, 1 Tim 2:5
This is simply an allusion to the Shema in Deut 6:4 and numerous others such as Isa 44:6, 45:5, 6, etc. See also 1 Cor 8:4, etc.
- God is Light, ὁ Θεὸς φῶς ἐστιν, 1 John 1:5
This is stating that God is in the category of beings whose essential being is light. John appears to use this is two senses: - God is literally light and God is the source of truth, the latter meaning that all spiritual truth surrounds the true identity of God.
- God is spirit, Πνεῦμα ὁ Θεός, John 4:24. Compare 2 Cor 3:18
This is a quintessential Hebraism to omit the verb "to be"; but the meaning is clear: God is in the category of beings that are "spirit". Other beings in this category include angels (Heb 1:14), demons (Luke 4:33, 8:2, 1 Tim 4:1, Acts 16:18, etc).
[We note that there is no question about what is the subject of this abbreviated sentence, because only theos/God has the article and pneuma/spirit does not.]
APPENDIX - One more?
There is also another "almost" category statement in the NT consiting of:
Heb 3:4 - For every house is built by someone, but the One having
built everything is God.
The last part of the sentence could be translated:
... God is the builder of everything.
However, the greek construction is not as simple as above and more elliptical.
Observations about the quoted texts. πνεῦμα ὁ θεός is very different from both ὁ θεός φῶς ἐστιν and ὁ θεός ἀγάπη ἐστίν. πνεῦμα ὁ θεός is a question about BEING. The other two are metaphors. This doesn't address your question. It is just a comment.
– C. Stirling Bartholomew Apr 13 '23 at 19:03