What is the use of the dative (Τῇ γὰρ χάριτί ἐστε σεσῳσμένοι) in Ephesians 2:8?
Dative of Cause (saved on the basis of faith) - Daniel Wallace
Dative of Means (saved by means of grace) - Lenski NT Commentary
Dative of Manner (saved graciously)
A dative of cause makes sense: the sense would be that grace is the foundation of or reason for salvation, which certainly harmonizes with other things that Paul says.