Thematic Bible: Why the law was given

Therefore as by the fall of one for all men to condemnation; so also by the justification of one for all men to justification of life. For as by one man's disobedience many were constituted sinful, so also by the obedience of one shall many be constituted just. And the law entered, that the fall might abound. And where sin abounded, grace superabounded: read more.
That as sin reigned in death, so grace might reign by justice to life eternal, through Jesus Christ our Lord.