Parashas Ki Sisa · Passuk 34:22
Torah Temimah points to classical source on this unit (verified).
English: “The Festival of Weeks” — the festival of the first fruits.
Derash on Shavuos and the Festival of Ingathering in the covenant.
And the Festival of Weeks you shall make for yourself, of the first fruits of the wheat harvest, and the Festival of Ingathering at the turn of the year.