Commentaries:
God commanded Israel, "Obey My voice." If we take that extremely literally, His voice would include only the Ten Commandments because He literally spoke only them in the hearing of all Israel. Nevertheless, "My voice" undoubtedly includes what He spoke privately to Moses, and thus what is contained within the terms given between Exodus 20 and 23.
John W. Ritenbaugh
The Covenants, Grace, and Law (Part Eighteen)