Why is keeping the law of Moses not necessary for salvation?

The law's purpose was never to provide salvation but to expose sin and our total inability to meet God's perfect standards. Romans 3:20 states that 'by the deeds of the law there shall no flesh be justified in his sight.' The apostles affirmed that if righteousness could be attained through the law, then Christ's death would have been in vain (Galatians 2:21). The law reveals God's holiness and our sinfulness, hence we are justified by faith in Christ alone, who fulfilled the law and offers His righteousness to all believers.