Andrew Murray emphasizes the significance of truly knowing the Holy Spirit, who is the Spirit of Truth and dwells within believers. He explains that spiritual knowledge is essential for experiencing the fullness of God's grace, and that understanding the Spirit's presence and work is crucial for a vibrant faith. Murray encourages believers to seek a deeper relationship with the Holy Spirit through prayer, obedience, and studying the Word of God, asserting that true knowledge of the Spirit leads to assurance and transformation. He highlights that the Spirit's indwelling is evidenced by a life of faith and obedience, and that knowing the Spirit is foundational for knowing Christ and the Father. Ultimately, Murray calls for a complete surrender to the Holy Spirit to fully experience His guidance and power in our lives.