Parashas Metzora · Passuk 14:17
Chabad.org — English translation + Rashi
Torah Temima points to Menachos 9b (verified on the daf).
E-Daf.com — Tsurras Hadaf (size=3)
HebrewBooks / Shas PDF of the daf
English: “And on the thumb of his hand …” — R’ Yirmiyah said to R’ Zeira: Why does the verse need both “on the thumb of his right hand” and “on the big toe of his right foot”? He replied: One comes to validate the sides, and one comes to invalidate the sides of the sides.
Precision of placement
Chazal define the acceptable area for the placement of the oil: the sides of the thumb/toe are valid, but the extreme outer edges are not.