Rashi on Exodus 24:7/רש"י על שמות כ״ד:ז׳

1ספר הברית THE BOOK OF THE COVENANT — the book which we have said contained the part of the Torah from בראשית till the “Giving of the Torah” including the Commandments that were given to them at Marah (Mekhilta; cf. Rashi on v. 4).