All those who read these pages will know by now if they didn't know before that righteousness comes only by faith.
The opposite is also true. The only ultimate source of sin is: unbelief.
John 16:8. Jesus said that the Holy Spirit will convict the world of sin, rightousness and judgment.
Then Jesus defines the specific sin in each of these three areas:
"... concerning sin because they do not believe in Me."
The primary sin, of which the whole world is guilty, is unbelief.