Theorem csbie

Description: Conversion of implicit substitution to explicit substitution into a class. (Contributed by AV, 2-Dec-2019)

	Ref	Expression
Hypotheses	csbie.1	$$⊢A\in \mathrm{V}$$
	csbie.2	$$⊢x=A\to B=C$$
Assertion	csbie	$$⊢⦋A/x⦌B=C$$

Proof

Step	Hyp	Ref	Expression
1		csbie.1	$$⊢A\in \mathrm{V}$$
2		csbie.2	$$⊢x=A\to B=C$$
3		nfcv	$$⊢\underset{\_}{Ⅎ}xC$$
4	1 3 2	csbief	$$⊢⦋A/x⦌B=C$$