TT #29 · Parshas Shemini · Aliyah 2 · Passuk 22
Chabad.org — English translation + Rashi
English: “He blessed them”: this blessing is initially unspecified, until the Torah explains it with “May Hashem bless you and guard you” in Parshas Naso.
Jerusalem Talmud, Taanis 4:1.
Gezeirah shavah — the unspecified blessing here is identified through the explicit priestly blessing in the Torah’s later passage.
The blessing here is left undefined until Numbers 6 supplies the formulation of Birkat Kohanim.