Isaiah 26:3

1 In that day shall this song be sung in the land of Judah; We have a strong city; salvation will God appoint for walls and bulwarks.

2 Open ye the gates, that the righteous nation which keepeth the truth may enter in.

Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee.

4 Trust ye in the LORD for ever: for in the LORD JEHOVAH is everlasting strength:

5 For he bringeth down them that dwell on high; the lofty city, he layeth it low; he layeth it low, even to the ground; he bringeth it even to the dust.

Do read the surrounding verses too, because the context often says more than a single verse.

Compare

BSB
You will keep in perfect peace the steadfast of mind, because he trusts in You.
KJV
Thou wilt keep him in perfect peace, whose mind is stayed on thee: because he trusteth in thee.
WEB
You will keep whoever’s mind is steadfast in perfect peace, because he trusts in you.
ASV
Thou wilt keep [him] in perfect peace, [whose] mind [is] stayed [on thee]; because he trusteth in thee.
DARBY
Thou wilt keep in perfect peace the mind stayed [on thee], for he confideth in thee.
BLB
You will keep the one steadfast of mind in perfect peace, because he trusts in You.
ÅB
Den som har et grunnfestet sinn, ham lar du alltid ha fred, for til deg setter han sin lit.
OTB
Du vil holde i fullkommen fred de som har et stødig sinn, fordi de stoler på deg.
B1930
Den som har et grunnfestet sinn, ham lar du alltid ha fred, for til dig setter han sin lit.

Study notes (Tyndale)

Original text and word study

Cross references