1 - God is who He is. (I am who am) His nature is Holy. This (His Holiness) is one of the ways we have been taught about Him; through scripture and by how He has chosen to reveal Himself to us.
2 - With His holiness (here I’m thinking “separate” or “other” for holy) we describe his nature as “other” or different than our nature.
3 - This definition of holy excludes what we know of as sin. As a Holy God, He doesn’t sin - He doesn’t covet, or not keep His day Holy, or blaspheme, or dishonor His parents

… His nature makes sinning contradictory to who He has told us He is. In this sense, He cannot sin.
So God is Holy. God is not sin.*
As God, Jesus became incarnate for us, to share all things with us. The mysterious duality of Jesus - fully God & fully human - is,
I believe, where the question “could Jesus sin?” becomes problematic. If I’m right, you’re where others have been throughout the centuries. (Sad note here: You’re not asking any new questions!

) Answering the question of the duality of Jesus incorrectly has led many people to heretical thoughts and some left the Church over these debates, so tread softly. How is Jesus (fully God; incapable of sin) abdle to be tempted? (Here we must be asking about His fully human nature.) Jesus being human is still Jesus. As man he does what we do, has emotions and expresses them, grows tired and sleeps, hungry and eats, etc., but He still is also God. He is still and always, holy.
I agree, this seems hard for me to comprehend! I, as a sinful human, only know my weaknesses and capacity to sin. Jesus, on the other hand, knows His nature and lack of sin. So when satan is on the scene – “don’t you want this?”, “we can bring the angels down to help here…”, etc., I think of how I would respond (in my sinful nature) and say, “how would I respond?” and the answer is likely, sinfully. Jesus, though tempted (the devil still offers the same things) responds as who He is, “naturally” (His nature) without sinning. He is tempted (“don’t you want this”) but not as I am tempted (“ooh, that sounds nice!”). His response is, “No, of course not” and then cites scriptures. He shows us how we
should be instead of how we’ve become.
Jesus says, this is how I Am - sinless, “God reliant” in all circumstances, even as a human. So is He tempted? Not like me. He has given over His nature to God the Father. (and don’t forget, even as man, He still is God!) I have not fully given myself to God. I have retained my nature to “be as god” when convenient. (For God knows that when you eat of it your eyes will be opened, and you will be like God, knowing good and evil. - Gen 3:5)
I hope this helps a little.
- One more thing, in the response I stated “So God is Holy. God is not sin.” Yet we know at one point, Jesus took up our sin - “For he has made him, who knew no sin, to be sin for us; that we might be made the righteousness of God in him.” (2 Cor 5:21) This, though, is another conversation!

Peace and Blessings
Steven