The law "was added because of transgressions" (Galatians 3:19) to make it clear what sin is--a transgression of the character and will of God. When people understand the nature of sin, it soon becomes clear that all people are sinners (Romans 3:10,12,23), and all need to come to Christ for forgiveness and salvation.

Source:

KJV Defenders Study Bible, by Dr. Henry Morris, Ph.D.
Publisher: Thomas Nelson
Language: English
DEF 10 ISBN 0-529-10444-x
DEF 10-1 ISBN 0-529-10445-8