Passage
By an assured purpose wilt thou preserue perfite peace, because they trusted in thee.
Isaiah 26:3 (GNV)
Nearby Context
Isaiah 26:1 In that day shall this song be sung in the land of Iudah, We haue a strong citie: saluation shall God set for walles and bulwarkes.
Isaiah 26:2 Open ye the gates that the righteous nation, which keepeth the trueth, may enter in.
Isaiah 26:3 By an assured purpose wilt thou preserue perfite peace, because they trusted in thee.
Isaiah 26:4 Trust in the Lord for euer: for in the Lord God is strength for euermore.
Isaiah 26:5 For hee will bring downe them that dwell on hie: the hie citie he will abase: euen vnto the ground wil he cast it downe, and bring it vnto dust.
Study Lenses
The verse centers on "purpose", "assured", "wilt", "thou", "preserue", "perfite", "peace", and "trusted". It is saying that the verse draws attention to "purpose" and "assured", so its meaning should be read from those terms before moving to application.
The nearby context moves from verse 2's "Open ye the gates that the righteous..." into verse 4's "Trust in the Lord for euer for...", so "purpose" and "assured" belong inside that flow. In Isaiah context, the local focus is the Holy One of Israel, judgment and restoration, the servant of the LORD, and Zion's hope.
A plain takeaway is to answer the verse's own emphasis on "purpose" and "assured" with trust shaped by these words, not by a vague optimism outside the passage.