Likutei Sichos – Vol 23 p 33 ff The argument that introduces this sicha’s question: Torah never changes. The faith that is needed to maintain this priority. Page 34.

Likutei Sichos – Vol 23 p 33 ff Post Mattan Torah Mitzvos are about and for [the unchanging] G-d also, while the pre Mattan Torah idea, being that it was for us, was flexible and dynamic. Page 33-4.

Likutei Sichos – Vol 23 p 33 ff Differences between the pre and post Mattan Torah. 1) It was given in its entirety to each Jew [all at once], 2) It was commanded and not done by volunteering, 3) Cannot change. The addition of Anochi changed all that. Page 33.

Likutei Sichos – Vol 23 p 33 ff Introduction to the beginning of the Sicha. The Avos kept Mitzvos with reason, like Goyim keep their seven laws of Noach. Page 33.

Introduction to the Sicha of Nitzchiyus HaTorah, The story behind it and its issues.