"Contradiction is the rule of the true."—G.W.F. Hegel
class="first">The real "Thesis - Antithesis - Synthesis"
This may not even be Fichte's oldest reference, but it comes from his Science of Knowledge, 1794 (Grundlage der gesammten Wissenschaftslehre) (translated by Heath & Lachs).
Maybe you could say Hegel got it from Fichte ... except that Hegel never says this!
The only place I know of where Hegel specifically mentions "T - A - S" is in the History of Philosophy (just before getting to Fichte) where he's talking about Kant:
This is the old Haldane & Simson (no p) translation, vol. 3, p. 477.
If you read the whole paragraph, you see Hegel is quite critical of this "triplicity".