Who said to ignore the Old Testament? Not Jesus.
1) “For truly, I say to you, till heaven and earth pass away, not an iota, not a dot, will pass the law until all is accomplished. Whoever then relaxes one of the least of these commandments and teaches men so, shall be called least in the kingdom of heaven; but he who does them and teaches them shall be called great in the kingdom of heaven.” (Matthew 5:18-19 RSV) Clearly the Old Testament is to be abided by until the end of human existence itself. None other then Jesus said so.
2) All of the vicious Old Testament laws will be binding forever. "It is easier for Heaven and Earth to pass away than for the smallest part of the letter of the law to become invalid." (Luke 16:17 NAB)