(1 Corinthians 11:25 NAS77) In the same way He took the cup also, after supper, saying, "This cup is the new covenant in My blood; do this, as often as you drink it, in remembrance of Me."As much as I consider myself a child of the new covenant, old contracts are not always voided by new ones. We have some grandfathered in.
We see it in technology. When the rotary dial was phased out in production it still worked for the old phones around. USB 1 still works in new computers with USB 2.
Jesus made a specific statement that applies to this.
(Matthew 5:17 KJV) Think not that I am come to destroy the law, or the prophets: I am not come to destroy, but to fulfil.So think of the Old Testament (covenant) as being a rotary dial. It worked and worked well. It was also slow and inflexible. Things have changed. We now have buttons and smart phones. Some people have special ring tones to tell them who is calling. We have call forwarding, texting and voice mail. The wires have even changed but the general concept of phone numbers and communication remain the same.
God is waiting to communicate with His people.
homo unius libri