God made Him who knew no sin to be sin on our behalf, so that in Him we might become the righteousness of God. – 2 Corinthians 5:21
We have sinned, and are separated from God because evil is completely contrary to His nature. Jesus took all of our sins upon himself, because he chose to be punished for us. He suffered the consequence of sin, death.
But when He rose from the dead He demonstrated that sin had been overcome, our sins were pardoned. And more than that, we have God’s uprightness through Jesus. We believe and through His grace we are accepted and forgiven, and God’s welcomes us into his family.