Go and learn what this means, “I desire mercy, and not sacrifice.” For I came not to call the righteous, but sinners. (Matthew 9:13 ESV)
God is actually merciful to everyone but he will not take away the penalty for sin. In the Old Testament, offering a sacrifice was the way people received the Lord’s forgiveness for their sins. They had to select an animal and kill it as a sin offering. The shedding of its blood and its death were meant to grab their attention and emphasize the seriousness of sin; hopefully, they would be so moved by this act with sorrow and be quick to repent. Unfortunately, this practice became a meaningless ritual; the people made animal sacrifices, but their hearts were not in it and they continued to sin.
We cannot fool God with words and rituals. He knows whether we are truly sorry or just going through the motions.
The good news is that he is patient and kind. He knows we are a work in progress and gives us the opportunity to change, that is, he gives us an incredible amount of grace and mercy.
First, Jesus paid the penalty for all of our sins by becoming the sacrifice for all mankind. Then he defeated death by rising back to life, which demonstrated his great power so that all who hear his story may believe that he is indeed God in the flesh. For those who believe, he inspires them to change with his love, guidance, and blessings.
God desires mercy because he loves sinners and he wants them (us) to be that way towards others. So instead of taking inventory of other people’s failures, he would rather have us withhold our judgment, work on ourselves, and then be an extension of his grace so they may one day another soul may come to know him and be saved.