I've heard this a lot around campus and in the classroom: all sin is equal in the eyes of God. It sounds really nice! But unfortunately, it's not true. I don't know why it's so often used in discussions on Scripture. There is some truth to it, but it's mostly not Biblical.
So to clear the air, here are two bits I've found that are quite helpful, I hope that you'll find them the same. One, a video from John Piper, and the other from Kevin DeYoung.
Every sin is not the same in God’s eyes.
This sentiment is popular with many Christians. For some it’s a sign of genuine humility–“I deserve God’s wrath too. So how can I judge someone else?” For others this is a way to dodge the hits that come when you dare to criticize trendy sins–“Yes, I do think mating with bovines is wrong, but it’s not worse than any other sin.” And for still others, it’s simply a soft form of relativism–“Those who live in glass houses shouldn’t throw stones, you know.”
Like many popular adages, this one about all sins being equal before God is not entirely wrong. Every sin is a breach of God’s holy law. And whoever fails to keep the law in one point is guilty of breaking all of it (James 2:10). So any sin committed against an infinite God deserves punishment. We’re all born sinners. We all sin. Every sin deserves death. That’s why the truism is half-true.
But it’s also a lot not true. Over and over the Bible teaches, either explicitly or implicitly, that some sins are worse than others.