
This isn’t an off handed comment from Piper. He has taught and defended this distinction for decades: justification is by faith alone, but final salvation/glorification is not. He made it explicit in his 2017 Desiring God article (“we are saved through that fruit and that faith”) and doubled down in the 2018 Ask Pastor John podcast (“We are justified by faith alone but we are not ultimately saved by faith alone”). The same framework appears in his teaching as far back as 2006.
If “through” applied to works concerns you when someone says “because of,” it should here too. Ephesians 2:8 uses that exact preposition for the instrument of salvation: saved by grace “through” faith. Scripture does not apply it to fruit.
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