Midrash su Levitico 14:15

6) (Vayikra 14:15) ("And the Cohein shall take from the log of oil, and he shall pour onto the Cohein's left palm.") "from the log of oil and he shall pour": If the log (vessel) lacks the necessary amount, (some of it having spilled): If before he poured it (on the Cohein's left palm), he may refill it; if after, he must bring another (log, the service) having begun. These are the words of R. Akiva. R. Yishmael says: If the log lacks before he places it (i.e., before he sprinkles [viz. Vayikra 14 verse 16]), he may refill it, (the service not considered as having begun until he sprinkles); if after, he must bring another (log, the service) having begun.

7) "and he shall pour onto the Cohein's left palm": It is a mitzvah (for one Cohein) to pour into another Cohein's palm; but if he pours into his own palm, it is valid." (Vayikra 14:16) ("And the Cohein shall dip his right finger from the oil on his left palm, and he shall sprinkle from the oil with his finger seven times before the L–rd.") "And he shall dip": and not wipe (the palm).

8) "And he shall dip … and he shall sprinkle": For every sprinkling a (separate) dipping. It is written here "his finger," and elsewhere (Vayikra 4:6), "his finger." Just as "finger" here indicates the most adroit ("meyumeneth") finger on his right hand, (this being the thrust of ("finger hayemanith"), so "his finger" there indicates the most adroit finger on his right hand (i.e., the index finger).