To abolish would mean to remove and replace the Law of Moses and the writings of the prophets (that is, the whole Old Testament) as God’s revelation of his will.
until everything is accomplished: This could mean to obey the Old Testament perfectly, complete their teachings, or fulfill their prophecies (see Matthew 1:22; 2:15, 17, 23). Jesus himself embodies everything the Prophets and the Law taught and expected. Now that Christ has arrived, who fulfills these writings, we must understand the Old Testament in relation to him (Luke 24:26, 44).