J. I. Packer, Keep In Step with the Spirit:
Holiness…is the fruit of the Spirit, displayed as the Christian walks by the Spirit (Galatians 5:16, 22, 25). Holiness is consecrated closeness to God. Holiness is in essence obeying God, living to God and for God, imitating God, keeping his law, taking his side against sin, doing righteousness, performing good works, following Christ’s teaching and example, worshiping God in the Spirit, loving and serving God and men out of reverence for Christ. In relation to God, holiness takes the form of a single-minded passion to please by love and loyalty devotion and praise. In relation to sin, it takes the form of a resistance movement a discipline of not gratifying the desires of the flesh but of putting to death the deeds of the body (Galatians 5:16; Romans 8:3). Holiness is, in a word, God-taught, Spirit-wrought Christlikeness, the sum and substance of committed discipleship, the demonstration of faith working by love, the responsive outflow in righteousness of supernatural life from the hearts of those who are born again.