When attempting to locate the exact placement of the sun in the heavenly layers (within the biblical narrative of creation), the specific detail of which heaven isn’t directly stated in the commonly accepted scriptures.
?? Genesis 1:16-17 gives us the general idea that the sun is in the firmament of the heavens:
– “Then God made two great lights: the greater light to rule the day, and the lesser light to rule the night. He made the stars also. God set them
in the firmament of the heavens 
to give light on the earth”
?? But which of the heavens? One hint we may be given is in the Revelation 12:1 vision of a woman in heaven clothed with the sun:
– “A great sign appeared in heaven: a woman clothed with the sun, and the moon under her feet, and on her head a crown of twelve stars”
??If this woman is indeed the “bride of the lamb” described as the New Jerusalem in Revelation 21:2-10 – and the “mother” as Paul calls the Jerusalem above in Galatians 4:26 – and the “mother who travails in labor” as the heavenly Zion is described in Isaiah 66:7-13… then it should be noted that this personified Paradise will be coming from her place in the third heaven as revealed in 2 Corinth. 12:2-4:
– “I know a man in Christ who fourteen years ago-whether in the body I do not know, or out of the body I do not know, God knows-such a man was caught up to the third heaven. And I know how such a man-whether in the body or apart from the body I do not know, God knows- was caught up into Paradise and heard inexpressible words, which a man is not permitted to speak.”
?? Therefore, it can be surmised that the greater light of the sun shines from close proximity to Paradise, the New Jerusalem, currently in the third firmament layer of heaven. However, another ancient writing may bear witness to the validity of this interpretation …
A book called 3rd Baruch, also known as the Greek Apocalypse of Baruch, survives in Greek and Slavonic manuscripts. Some scholars suggest there was an earlier volume of this writing with Semitic origin that was later revised and distorted with insertions. In light of this and a few of the ideas the currently available text contains, it cannot all be deemed the inspired words of a prophet. But, we can consider that it may serve as a representation of the understanding and mindset from a pre – 4th century A.D. author.
3 Baruch 7:2
And the angel said to me, “Listen, Baruch: All things whatsoever I showed you are in the first and second heaven, and in the third heaven the sun passes through and gives light to the world.