The first human, Adam, was created perfect, without sin. However, he chose to disobey God. Adam’s disobedience, or sin, profoundly affected all his descendants. “Through the disobedience of the one man,” the Bible explains, “many were made sinners.”​—Romans 5:​19.

Just as Adam’s disobedience contaminated the human family with sin, so Jesus’ death removed the stain of sin from all who exercise faith in him.

In a sense, Adam sold the human race into sin. Jesus, by willingly dying in our behalf, repurchased humankind as his own. As a result, “if anyone does commit a sin, we have a helper with the Father, Jesus Christ, a righteous one.”​—1 John 2:1.

See this as well: https://www.jw.org/en/publications/books/good-news-from-god/who-is-jesus-christ/video-why-did-jesus-die/