If we ask the New Testament authors, “What is the nature of the Spirit’s work?” we receive a plethora of information. It is the Holy Spirit, for example, who is the One who makes God’s love real for us—”God’s love has been poured into our hearts through the Holy Spirit” (Rom. 5:5). In a sense, it is He who stands at the threshold of the Christian life, for only He can enable us to embrace Christ as Savior and Lord—”no one can say, ‘Jesus is Lord’ except in the Holy Spirit” (1 Cor. 12:3). Then, it is the Spirit who gives us the boldness to come into the presence of the awesome and almighty Maker of heaven and earth and call Him “Dear Father”—”God has sent the Spirit of his Son into our hearts, crying, ‘Abba! Father!’” (Gal. 4:6). It is the Spirit who enables believers, from various racial, social and religious backgrounds, to find true unity in Christ and together worship God (Eph. 2:18). In fact, without the Spirit, worship and the glorification of Jesus Christ cannot take place (Phil. 3:3). And it is the Spirit who is the true Guarantor of orthodoxy (2 Tim. 1:14).
An excellent summary statement of the range of the Spirit’s work is Galatians 5:25, which speaks so plainly about the Spirit as the Source from which we are to live our lives: “If we live by the Spirit, let us also walk by the Spirit.” The Spirit thus undergirds and empowers the entirety of our lives as Christians. To paraphrase John 15:5: apart from the Holy Spirit, we can do nothing of any true eternal value.
—Michael A. G. Haykin, The God Who Draws Near: An Introduction To Biblical Spirituality, xix-xx