Corollary 1
Tag 0BA9, permanent. Cite it as [Bourbaki, Tag 0BA9].
General Topology, chapter I, § 10. Proper mappings
If is a proper mapping, then the restriction of to a closed subset of is a proper mapping of into .
For this restriction is the composition , where is the canonical injection, which is proper by Proposition 2.
Bourbaki puts the proof directly after the statement, so what is above is the statement and its proof together.