Thematic Bible: Why the law was given

Hence then, as through one fault, the sentence was unto all men unto condemnation, so, also, through one recovery of righteousness, the decree of favour is unto all men for righteous acquittal unto life; For, just as, through the disobedience of the one man, sinners, the many were constituted, so, also, through the obedience of the one, righteous, the many shall be constituted - Law, however, gained admission, in order that the fault might abound, but, where the sin abounded, the favour greatly superabounded: read more.
In order that - just as sin reigned in death, so, also, favour, might reign through righteousness unto life age-abiding, through Jesus Christ our Lord.