How do we know that man's heart is evil?

In Romans 3, Paul illustrates the depth of human sinfulness by stating that there is none righteous, no, not one. He describes humanity as having open sepulchers for throats, using deceptive speech, and being full of cursing and bitterness. This sinful condition is not merely about actions but is rooted in the heart, which manifests itself through our words. The tongue's deceitful nature epitomizes this reality, reinforcing the belief that our speech reveals the wickedness within us. Thus, it is through scripture that we see the genuine state of man's heart.