Parashas Behar · Aliyah 1 · Passuk 25:01
Chabad.org — English translation + Rashi
Torah Temimah cites Sifra (Torat Kohanim) Behar, Section 1.
English: “At Mount Sinai.” What is the connection of Shemittah to Mount Sinai? Were not all the mitzvos stated at Sinai? Rather: just as Shemittah was stated with its general principles and its details at Sinai, so too all the mitzvos were stated with their general principles and their details at Sinai.
Classical derasha (Sifra) — from the apparently superfluous location “at Mount Sinai” applied to the laws of Shemittah.
Every mitzvah of the Torah was given at Sinai together with both its general principles and its detailed laws. The mention of Shemittah at Sinai teaches the pattern for the entire Torah.