Corollary 2
Tag 0A44, permanent. Cite it as [Bourbaki, Tag 0A44].
Lie Groups and Lie Algebras, chapter II, § 3. Enveloping algebra of the free Lie algebra
If is a field of characteristic 0, is the Lie algebra of primitive elements of .
This follows from Corollary 1 and the Corollary to Proposition 9 of § 1, no. 5.
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.