Philippians 4:6-7

6 In nothing be anxious, but in everything, by prayer and petition with thanksgiving, let your requests be made known to God.  7 The peace of God, which surpasses all understanding, will guard your hearts and your thoughts in Christ Jesus.

Colossians 3:14-16

14 Above all these things, walk in love, which is the bond of perfection.  15 And let the peace of God rule in your hearts, to which also you were called in one body; and be thankful.  16 Let the word of Christ dwell in you richly; in all wisdom teaching and admonishing one another with psalms, hymns, and spiritual songs, singing with grace in your heart to the Lord.