Parashas Vayikra · Aliyah 2 · Passuk 1
Chabad.org — English translation + Rashi
Torah Temima points to Menachot 104b on the phrase korban minchah.
E-Daf / Tsurras Hadaf
PDF of the daf / source
English: “An offering, a meal-offering” — this teaches that one may volunteer oil alone.
Yittur lashon (superfluous wording) — the extra word korban beside minchah is not needed for the plain sense and is therefore available for derashah.
One may donate oil by itself as a freewill gift (not less than a log), even without flour. The doubled language “korban minchah” opens the door to volunteering components of the meal-offering separately.