26:3 perfect peace. The peace described here is first the corporate peace of the city (v. 1) and the nation (v. 2) that comes from the “hand of the Lord” (25:10); but it is also the individual peace of the person whose mind is stayed on God. The source of such peace is the righteous, sovereign, saving God (25:9)—who “will swallow up death forever” and “will wipe away” every tear (25:8; cf. Rev. 21:4), and who alone is worthy of trust. (On the meaning of peace in the OT and NT, see note on John 14:27.)
26:3 You will protect a firm inclination in peace, in peace The righteous can count on peace instead of war, destruction, and judgment as long as they continue to trust in Yahweh. Judgment came because they did not fully trust in Yahweh.
The major sin and folly of Judah (and all the nations) was placing trust in themselves and their own power rather than trusting in and acknowledging Yahweh’s power. The theme of judgment throughout Isaiah is intimately linked with the theme of human pride and arrogance.
26:3 perfect peace. The peace of God that the righteous receive and promote (v. 12; 32:17, 18; 55:12; 66:12) will not be extended to the wicked (48:22; 59:8). This peace is found in Immanuel (9:6; 11:6–9; 14:7 and notes). As the previous chapters make clear, it is not a peace that stems from the absence of difficulties; rather, it is a peace that guards their hearts and minds in the midst of great trials.
stayed … trusts. See 2:22; 8:12, 17.
 Crossway Bibles. (2008). The ESV Study Bible (p. 1285). Wheaton, IL: Crossway Bibles.
 Barry, J. D., Mangum, D., Brown, D. R., Heiser, M. S., Custis, M., Ritzema, E., … Bomar, D. (2012, 2016). Faithlife Study Bible (Is 26:3). Bellingham, WA: Lexham Press.
 Sproul, R. C. (Ed.). (2015). The Reformation Study Bible: English Standard Version (2015 Edition) (pp. 1165–1166). Orlando, FL: Reformation Trust.