Why are all sins ultimately against God?

TL;DR:

All sins are ultimately against God because He is the ultimate authority, the perfect One, and the rightful judge. Through Jesus’ sacrifice, all sin can be forgiven and our relationship with God can be restored.

what does the bible say?

Sin is ultimately against God because His law reflects His holy nature, and breaking it is a personal offense against Him (1 John 3:4; Romans 3:23). Even when sins harm others, they are first and foremost violations of God's commands, as seen in David's confession (Psalm 51:4) and Joseph’s refusal to sin (Genesis 39:9). Since God is the ultimate authority, sin is a breach of faith against Him, and He alone is the rightful judge (Leviticus 6:2; Acts 17:30-31). Just as crimes are prosecuted by the state rather than the victim, sin is judged by God, who has appointed Christ as the final judge (Ezekiel 18:4; John 5:22). Through Jesus’ sacrifice, all sin can be forgiven, offering believers salvation and escape from God’s righteous judgment (Ephesians 2:8-10).

from the old testament

Since God's law is a reflection of His holy nature, to sin by transgressing His law is to offend Him personally. This point is illustrated for us in the narratives concerning David's sin of adultery and murder as well as the temptation of Joseph by Potiphar's wife (Psalm 51:4; Genesis 39:9). Although adultery and murder are clearly sins against other people, both David and Joseph viewed them to be primarily against God Himself.
Sin against a neighbor is described as a breach of faith against the Lord (Leviticus 6:2).
Since God is the ultimate authority over all people, sin is an offense against Him (Ezekiel 18:4).

from the new testament

God is the rightful prosecutor and judge (Acts 17:30-31).
Sin is a transgression of God's law (1 John 3:4; Romans 4:15).
Sin, by its very definition, is against God because to sin means either to violate God's prohibitive commands or to omit practicing His positive commands (James 4:17).
Sin is defined in relation to God's glory, showing that every sin is an offense against Him (Romans 3:23).
Just as every sin is ultimately against God, every sin can be ultimately forgiven because of God's gift of Jesus Christ (Matthew 26:28; John 4:10; Ephesians 2:8-10).

implications for today

We sin against others by doing to them what God has forbidden or by failing to do to them or for them what God has commanded (Matthew 22:39; James 2:8). The commands do not come from others but from God. Therefore, the sin is first and foremost against Him. An analogy can be seen in criminal law. When a person commits a crime against another person, he or she has violated not only that person but the law of a state or country primarily. This is why it is the government, not the individual, who has been harmed, who is named in the legal caption (e.g. The State of Florida vs. Mr. Jones). The government prosecutes and executes judgment. Likewise, when we sin against others, we are transgressing, not their law, but God's law. Therefore, God is the rightful prosecutor and judge (Acts 17:30-31). God has appointed His Son, Jesus Christ, to carry out this judgment (John 5:22). By believing in Jesus Christ's sacrificial death and glorious resurrection, we are saved. We escape God’s just wrath against sin by believing that God has washed us clean of every sin we have and will commit against Him based on the substitutionary atoning death of His Son (1 Thessalonians 1:9-10).

understand

Since the law reflects God’s holy nature, any violation of it is a personal offense against Him.
Sin is judged by God, the rightful judge.
Every sin can be forgiven through Christ, restoring our relationship with God.

reflect

How does recognizing that all sin is ultimately against God change the way you view your actions and motivations?
How have you experienced God's forgiveness for sins you committed against Him, and how has that shaped your relationship with Him?
How can you remind yourself that sin is not just a breach against others but a violation against God, and how does this understanding impact your behavior?

engage

How can we help others understand that sin is ultimately against God, not just a wrongdoing against people or society?
What is the significance in understanding that all sin is ultimately against God, and how does that impact the way we respond to our sin?
How does the biblical analogy of criminal law (where the state prosecutes a crime) help us better understand why God is the rightful prosecutor and judge of sin?