To add more ...
1. Context: Encounter with the Samaritan woman (there is true and false worship; cf. will worship, entertainment; formalism; superstition, etc.)
2. Initiative: The Father does the seeking (4:23b.)
3. The Messianic Cross: v.23 makes reference to 'the hour'; a Johannine reference to the Cross! of the Messiah (vv.25f.) who Himself is the truth. The very idea, of course, is repudiated by the natural man, however religious he may be, see 1.Cor.1f. .
4. 'Must' - means necessary.
In essence, true worship is Christ- / Cross-centered rather than man-centered. I fear that is the missing element, and it is just possible to imagine a Christ-less Church, see Rev.3:20.
And here is a good audio
sermon by Eric Alexander.