TT #146 · Parashas Shoftim · Third Aliyah · Passuk 18:04
The first of your grain, your wine, and your oil, and the first of the fleece of your flock, you shall give to him.
Torah Temimah points to Sifrei Devarim 166.
TT lemma: רֵאשִׁית דְּגָנְךָ תִּירֹשְׁךָ וְיִצְהָרֶךָ.
English: ‘The first of your grain, wine, and oil’ – from ordinary produce and not from consecrated produce.
Derash excluding sacred produce (Sifrei) — the gifts come from ordinary ownership.
Terumah is separated from ordinary (chullin) produce, not from produce that is already consecrated.