How do we know sin is a principle in our hearts?

Scripture teaches that sin is not just about actions or words, but it is a pervasive principle that resides within our hearts. Romans 3:23 declares, 'For all have sinned and fall short of the glory of God,' highlighting that sin originates from our nature. Jesus affirms this understanding in Mark 7:21-23, where He teaches that evil thoughts and actions come from within. Therefore, recognizing this principle of sin is fundamental to understanding our need for Christ's redeeming work, which addresses our heart condition, not just external behaviors.