“God is a Spirit: and they that worship him must worship him in spirit and in truth.”
King James Version (KJV)
4:24 God is a Spirit - Not only remote from the body, and all the properties of it, but likewise full of all spiritual perfections, power, wisdom, love, holiness. And our worship should be suitable to his nature. We should worship him with the truly spiritual worship of faith, love, and holiness, animating all our tempers, thoughts, words, and actions.
Joh 4:24 God [is] a Spirit. Rather, "God is Spirit". This declaration is fundamental. Since he is Spirit, he must receive spiritual worship, and is everywhere present.