Theorem nfsab1OLD

Description: Obsolete version of nfsab1 as of 20-Sep-2023. (Contributed by Mario Carneiro, 11-Aug-2016) (Proof modification is discouraged.) (New usage is discouraged.)

	Ref	Expression
Assertion	nfsab1OLD	$$⊢Ⅎxy\in \left\{x|\phi \right\}$$

Proof

Step	Hyp	Ref	Expression
1		hbab1	$$⊢y\in \left\{x|\phi \right\}\to \forall xy\in \left\{x|\phi \right\}$$
2	1	nf5i	$$⊢Ⅎxy\in \left\{x|\phi \right\}$$