Is one sin worse or greater than another? Isn't all sin the same in God's eyes?
Many have asked this question, me included. To find the answer we have to consider several truths.
First, all sin is equal in the sense that all sin breaks God's law and falls short of His perfect standards. The Bible portrays sin as straying from God's paths—it is opposing Him; it is rebellion. Whether it is the sin of stealing a small item, telling a lie, or murder, all sin transgresses the law of God. In that sense all sin is the same in God's eyes. Human law parallels this: a person can break the law by jaywalking or by mass murder. Either way, the law is violated.
The second truth to consider is the personal and social consequence of sin. In human law, jaywalking does not have the same personal and social impact and consequence as committing murder. Similarly the Bible also teaches that not all sin is equal in its personal, social, spiritual, and eternal impact. The sins David committed in connection with his adultery with Bathsheba had a far greater negative personal, social, spiritual, and eternal impact than the lie told by Rahab to protect the Israelite spies (Joshua 2:1-7). Measuring it that way, some sins are obviously greater than others.
This has implications in light of a third thing to consider: God's justice. The justice of God requires He render to everyone that which is due them, both good and bad—reward or punishment (2 Corinthians 5:10). And justice requires that rewards and punishment must be commensurate with the deeds. Greater sin requires greater punishment or else it isn't just.
In Matthew 11:21-22 Jesus says, “Woe to you, Chorazin! Woe to you, Bethsaida! For if the miracles that were performed in you had been performed in Tyre and Sidon, they would have repented long ago in sackcloth and ashes. But I tell you, it will be more bearable for Tyre and Sidon on the day of judgment than for you.” Chorazin and Bethsaida were places Jesus did miracles and therefore gave more light concerning His identity. But the people didn't repent of their unbelief. Jesus indicates how punishment would be worse for unbelievers of Chorazin and Bethsaida because they have been given more light (Jesus' miracles) than those in Tyre and Sidon. They were accountable for more.
In God's mind the sin of Chorazin and Bethsaida was worse and therefore required greater punishment. Unbelievers who commit greater sin in this life receive greater punishment in eternity. That is why the books are opened at the judgment—to weigh their lives “according to their deeds” and to measure appropriate punishment (Revelation 20:12–13). Acceptance or rejection of Christ's work on the cross determines destiny of heaven or hell. Judgment of the deeds determines degree of punishment.
When it comes to believers God will reward the deeds done in this life. Our destination of heaven is already settled by owning Christ as Saviour. We are already justified by faith (Romans 5:1) and for the believer there is no condemnation or punishment (8:1). But the issue of rewards in heaven is yet to be settled at the Judgment Seat of Christ (2 Corinthians 5:10). Some believers will receive great reward in heaven (Matthew 6:1,4; Luke 6:23) while others would be saved “yet so as by fire.” That is, being saved but with no rewards to show (1 Corinthians 3:14-15). Some will show faithfulness in this life and be granted even greater responsibility in heaven, while those who weren't faithful will lose any reward they might have had (Matthew 25).
Accepting or rejecting Christ determines destiny. How we live—choosing to sin or not, and the kind of sin we engage in—matters now, and for eternity. While every sin breaks God's standards, not every sin is consequentially the same. How we live counts forever.
I hope this helps.