Andrew Murray opens his Introduction to the book with these words: "The message which this little book brings is simple but most solemn. It is to the effect that the one thing needful for the Church, and the thing which, above all others, men ought everywhere to seek for with one accord and with their whole heart, is to be filled with the Spirit of God."

Jesus said "He that believeth on Me, as the Scripture hath said, out of his heart shall flow rivers of living water". In Murray's words, it is as we yield our hearts to the leading of the Holy Spirit to know Christ and look at Him, and believe in what is revealed, that the Spirit can take possession of us. The Spirit is given to reveal Christ, and every revelation of Christ fully accepted gives the Spirit room to dwell and work within us. Thus can the promise of Jesus be fulfilled and we can be led into a life in which we fully trust in Christ and in which we know the fullness and power of the Spirit.