It is in regards to having The Holy Spirit of promise as our guide, working inside us and listening to Him, instead of having only brain knowledge of God's laws.
The Holy Spirit can guide and direct us in ways that Bible text cannot. But it will always agree with God's Holy Writ.
Some today who claim to have power by The Holy Spirit are claiming some very crazy things are of The Spirit when they are not. In that sense, study of God's Holy Writ becomes important too, because it will help reveal a true working of The Holy Spirit.