"Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil. For verily I say unto you, Till heaven and earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled. Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven: but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven." Matthew 5:17-19 KJV

Keep the commandments! All prophesies of the Old Testament haven't been fulfilled as of yet, which means that the law still stands (think Isaiah, Daniel). Don't misunderstand Paul's writings, which Peter himself attests to being difficult to understand. The law still stands!

"Do we then make void the law through faith? God forbid: yea, we establish the law." Romans 3:31

"Because the law worketh wrath: for where no law is, there is no transgression." Romans 4:15

"For until the law sin was in the world: but sin is not imputed when there is no law." Romans 5:13

"For sin shall not have dominion over you: for ye are not under the law, but under grace. What then? shall we sin, because we are not under the law, but under grace? God forbid." Romans 6:14-15

"Whosoever committeth sin transgresseth also the law: for sin is the transgression of the law." 1 John 3:4

"The sting of death is sin; and the strength of sin is the law." 1 Corinthians 15:56

We need the law to define sin! If we don't need to keep the law, then what is sin?