Isa 26:3-4, 3 You will keep him in perfect peace, whose mind is stayed on You, Because he trusts in You. 4 Trust in the Lord forever, For in Yah, the Lord, is everlasting strength.
The Peace in God is continuous. It’s the assurance of God’s presence at all times. This peace has little or no feelings associated with it. This is based on the knowledge of God, that He can be trusted.
God keeps His people, whose mind stay on him, in perfect peace. Why? Because, they “Trust in the Lord forever, For in Jehovah, the Lord, is everlasting strength” (Verse 4). To trust means that if You can’t see His hands, then you can trust His heart, in all seasons. This was Paul’s prayer for this kind of peace: “May the God of hope fill you with all joy and peace in believing, so that by the power of the Holy Spirit you may abound in hope.” (Rom 15:13).
God’s word to Joshua with Moses dead was to “be strong and be courageous”. God was not giving Joshua new weapons or battle plan. Peace and confidences would come through the knowledge of God’s promised presence (shield) all the days of his life (Jos 1:5, 9, 17). Faith leads to joy and peace, which produces the confident anticipation of future hope and progressive good. Believers are held by God’s perfect peace when their minds stay in Him in the word and prayer, Jos 1:8, “This Book of the Law shall not depart from your mouth, but you shall meditate in it day and night, …”