What is the peace that passes all understanding (Philippians 4:7)?

from the old testament

• True peace comes from God. Speaking about a future praise to God for peace, Isaiah wrote, “You keep him in perfect peace whose mind is stayed on you, because he trusts in you” (Isaiah 26:3). The one who trusts in God receives perfect peace. Not through knowledge but through confidence that God is in control.
• The peace of God is not what the world considers peace. It is not peace from adversity but peace through it. The sons of Korah exemplified this, saying, “God is our refuge and strength, a very present help in trouble. Therefore we will not fear though the earth give way, though the mountains be moved into the heart of the sea, though its waters roar and foam, though the mountains tremble at its swelling” (Psalm 46:1–3).
• Because God is the source of true peace, His people are called to “cast your burden on the LORD, and he will sustain you; he will never permit the righteous to be moved” (Psalm 55:22).
• One can have such peace because the world is not operating on its own. Rather, God is sovereign over it. God is like no other, “declaring the end from the beginning and from ancient times things not yet done, saying, ‘My counsel shall stand, and I will accomplish all my purpose,’” (Isaiah 46:10). Because He is in control of everything, believers are to “Be still, and know that I am God” (Psalm 46:10a).

from the new testament

• In the letter to the Philippians, Paul touches on several issues that had caused and were causing them anxiety. This included Paul being in prison and what that meant for the gospel (Philippians 1:12–13), being frightened by enemies of Paul and the gospel (Philippians 1:27–28), worried about the health of their beloved Epaphroditus (Philippians 2:25–27), and a fight between two prominent Christian women (Philippians 4:2).
• Regarding all this and more, Paul said, “The Lord is at hand; do not be anxious about anything, but in everything by prayer and supplication with thanksgiving let your requests be made known to God. And the peace of God, which surpasses all understanding, will guard your hearts and your minds in Christ Jesus” (Philippians 4:5b–7).
• He first reminded them that “the Lord is at hand,” referring to Jesus’ imminent return. He reminded them that, though there were frightening things in the world, Jesus was coming and would set all things right (cf. Revelation 21:4).
• He then told them the solution to anxiety was prayer. It was going to God and, as Peter said elsewhere, “casting all your anxieties on him, because he cares for you” (1 Peter 5:7). Prayer is the expression of trust in God by telling Him what is worrying and what one needs to get through whatever the current issue is, and then leaving it to God to handle.
• The result of remembering Jesus and returning to and trusting in God through prayer was “the peace of God, which surpasses all understanding.” Paul was saying that God’s peace doesn’t come from knowledge of the future, but from trusting that God handles it, even when one doesn't know how it will all work out. The peace is grounded in knowing God is in control and that “for those who love God all things work together for good, for those who are called according to his purpose” (Romans 8:28).
• Paul said that that kind of peace will “guard your hearts and your minds in Christ Jesus.” Remembering that Jesus is coming and will set all things right guards the believer from entering into a downward spiral of worry about the future.
• Paul then closes by saying, “whatever is true, whatever is honorable, whatever is just, whatever is pure, whatever is lovely, whatever is commendable, if there is any excellence, if there is anything worthy of praise, think about these things” and “practice these things, and the God of peace will be with you” (Philippians 4:8, 9b). The peace of God comes through prayer and by actively not being anxious, filling one’s mind with the goodness of God and praiseworthy things.

implications for today

If we knew what was going to happen tomorrow, we wouldn’t be anxious about it. That is peace from understanding. But when we have peace despite not knowing what tomorrow brings, that is peace that surpasses understanding. It’s peace that is not grounded on knowing what will happen. However, for that peace to be true peace, it must be grounded on the truth that God is capable of handling tomorrow’s cares.

And He is not only capable, but He alone can handle our cares. He is all-powerful. He is sovereign. He is already present in the future that you have not yet reached. Nothing you will face will surprise Him, overwhelm Him, or fall outside of His sovereign control. He possesses all wisdom when you don't know what to do, all power when you are too weak to carry the burden, and perfect love when fear tells you that you are alone.

Trusting God does not mean believing tomorrow will be easy or free from suffering; it means believing that whatever tomorrow holds, God will be sufficient for it. Because He is faithful to keep His promises, work all things for the good of those who love Him, and never leave or forsake His children, you can release the need to control the future and rest in the One who already holds it.