The subject involves food and drink offerings and various washings imposed until the time of reformation—not the entirety of God's law. In His mind's eye, whenever He gave them these rituals, there was a grandfather clause. A grandfather clause is stipulation attached to a law that causes it to expire either under certain conditions or at a certain time. These rituals were imposed until the time of reformation. This is the grandfather clause. These requirements, legally forced on the Israelites, were to last only for a certain period of time.
Jeremiah 7:22-24 says that when these people made the covenant with God, He did not speak about sacrifices. He only said, "Obey My voice." However, because they transgressed, something was added—imposed on them. It was as though these rituals were a penalty because they transgressed God's voice, yet it was to last only for a certain period of time.
This is similar in concept to what we have today when a convicted person is required to check in with a parole officer for a given number of years, sentenced to perform a certain number of hours of community service, or ordered to attend certain classes and to refrain from engaging in particular privileges for a stipulated period.