Parashas Metzora · Passuk 14:15
Chabad.org — English translation + Rashi
Torah Temima points to Negaim 14:10.
English: “Onto the palm of the kohen” — it is a mitzvah that he pour into the palm of his fellow [kohen]; yet if he poured into his own palm he has still fulfilled the obligation.
Preferred vs. valid procedure
Chazal prefer that one kohen pour into the palm of another, but pouring into one’s own palm is also valid.