In Isaiah 26:1–4 we read,
In that day this song will be sung in the land of Judah: “We have a strong city; [Elohim] will appoint salvation [Heb. Yeshua] for walls and bulwarks. Open the gates, that the righteous nation which keeps the truth may enter in. You will keep him in perfect peace, whose mind is stayed on You, because he trusts in You. Trust in YHVH forever, for in YAH, YHVH, is everlasting strength.
My commentary on verse 3:
Isaiah 26:3, Peace. Heb. shalom. This word is spelled in its undiminished form (shin, lamed, vav, mem sofit) here containing the Hebrew letter vav (as opposed to other places in the Hebrew Scriptures where shalom is spelled deffectively [shin, lamed, mem sofit] without the letter vav denoting an incomplete or human-originated peace).
This verse is referring to that deep and inner soul-quenching peace of Elohim that passes all understanding that comes through a relationship with Yeshua the Messiah (Phil 4:7)—the fruit of the Spirit, as opposed to human or earthly, temporal peace. This peace comes because of our salvation through Yeshua, which is our spiritual bulwark and wall as stated in verse one. This is the same peace that Yeshua talked about when he said, “Peace I leave with you, My peace I give to you; not as the world gives do I give to you. Let not your heart be troubled, neither let it be afraid” (John 14:27).
If you don’t know this peace that calms the storms in your heart and mind, forgives sin, takes away all one’s shame and guilt and replaces it with love, joy, peace, hope and assurance of eternal life after you die, then now is the time to put your faith in Yeshua the Messiah, repent of your sins and love and obey him for the rest of your life.