“must worship in spirit and truth.” Here in John 4:24, Jesus spoke of the time coming in the future when God’s gift of holy spirit would be poured out upon all believers, and they would worship “in spirit and truth” at that future time (see commentary on John 4:23).
“spirit.” God is “spirit,” that is, He is an immaterial substance. The word “spirit” has many meanings. This is true in English, and also true in Hebrew (ruach = spirit) and Greek (pneuma = spirit). The Greek noun pneuma comes from the verb pneō, “to blow or breathe.” Thus, to the ancient Greeks, pneuma was “breath,” and it came to be associated with invisible things that exerted a force or power. Although pneuma is a noun, it is a “verbal noun,” (a noun that has the inherent characteristics of a verb or is grammatically related to a verb), so pneuma is always associated with the invisible power exercised by it. The word “wind” is a good example of a verbal noun, a noun that cannot be divorced from the power or force associated with it. There is no such thing as “wind” without action, even though “wind” is a noun. Similarly, pneuma is associated with its action or power. In fact, a good basic definition of pneuma, “spirit,” is something invisible that exerts a force. That is why some of the things that are called “spirit” in the Greek language are: God (John 4:24); the gift of God known as holy spirit (Acts 2:38); angels (Heb. 1:14); demons (Matt. 8:16); “breath” or “life” (Luke 8:55); wind; and attitudes, thoughts, or emotions (Matt. 26:41). All of these things are invisible but exert force or power.
[For more information on “spirit” and its different uses, see Appendix 6: “Usages of ‘Spirit.’”]