Now, before we get to “worship … in truth,” we need to dispose of some baggage. It’s been routinely taught that “worship in spirit” means to worship with the right attitude and “worship … in truth” means to worship according to the right rules.
The point Jesus is supposedly making is that the Samaritans  had the right heart but the wrong rules, whereas the Jews had the right rules but the wrong heart. Thus, Jesus is supposedly saying that, in Christianity, we must have both the right rules and the right heart.
This line of thinking goes back, I think, to early Calvinism and reaches the Churches of Christ via Puritanism, that same heritage that brought us the Regulative Principle of Worship (if it’s not authorized, it’s sin).
The admittedly sarcastic presentation in the footnote demonstrates the attitude that this understanding of “truth” promotes. We take our favorite doctrine — the one that distinguishes us from other believing communities — and insist that this “truth” separates the lost from the saved.
But the whole argument collapses upon investigation. Jesus did not say that the Samaritans had the right heart. It’s just not in the text. Indeed, the Samaritan woman seems to have a heart that utterly misunderstands Jesus’ message. The point of the passage is not that the Samaritans have better hearts than the Jews.
In fact, the Samaritans weren’t worshiping at all, because their temple had been destroyed two centuries earlier and was never rebuilt! This hardly evidences the right heart.
Jesus does indeed say that the Jews worshiped in the right location, but he’d just cleansed the Temple. It’s hardly the point of John’s Gospel that the Jews followed the right rules in their Temple worship! Rather, Jesus merely credited the Jews with worshiping in the right spot on the planet.
No, the meaning of this passage won’t be found in Puritanism. Rather, we need to let real history and the real context speak to us. And we should especially ask, how is the word “truth” used in John? Does the author help us to understand Jesus’ words?
“Truth” translates aletheia, found 24 times in John. It’s obviously a significant theme.
(John 3:21 ESV) But whoever does what is true comes to the light, so that it may be clearly seen that his works have been carried out in God.”
Do do “what is true” is to “come to the light.” Obviously, to do truth is to believe the gospel (John 3:18 is the context).
(John 5:33 ESV) 33 You sent to John, and he has borne witness to the truth.
John testified that Jesus is the Messiah (John 1:15). This is, of course, the core of the gospel.
(John 8:30-32 ESV) 30 As he was saying these things, many believed in him. 31 So Jesus said to the Jews who had believed him, “If you abide in my word, you are truly my disciples, 32 and you will know the truth, and the truth will set you free.”
To know the truth is to believe in Jesus. Faith in Jesus brings freedom.
(John 14:5-6 ESV) 5 Thomas said to him, “Lord, we do not know where you are going. How can we know the way?” 6 Jesus said to him, “I am the way, and the truth, and the life. No one comes to the Father except through me.”
Jesus is the truth, because the gospel is centered on Jesus.
(John 15:26 ESV) 26 “But when the Helper comes, whom I will send to you from the Father, the Spirit of truth, who proceeds from the Father, he will bear witness about me.”
The Holy Spirit is the Spirit of truth because the Spirit testifies about Jesus.
(John 18:37 ESV) 37 Then Pilate said to him, “So you are a king?” Jesus answered, “You say that I am a king. For this purpose I was born and for this purpose I have come into the world — to bear witness to the truth. Everyone who is of the truth listens to my voice.”
The truth is that Jesus is a king, that is, the Messiah.
To worship “in truth” does not mean “by the right rules.” That’s foreign to the context. Rather, true worship is thus worship that is all about and driven by the gospel, that is, the Messiahship of Jesus. 
Of course, to worship “in Spirit” is to worship as a possessor of the Holy Spirit, whom all who believe in Jesus receive.
Thus, “Spirit” and “truth” are parallels. Those who believe the truth receive the Spirit of truth. They become “of the truth.” They are in Jesus and hence enjoy “the way, the truth, and the life.” The have salvation and eternal life.
So how do we do this? Well, Jesus plainly says that the old form of worship — carrying an animal to the priest to be sacrificed — is replaced by the Truth. Jesus is our sacrfice. No more atoning sacrifice is required. Indeed, as Paul explains in Rom 6 and Rom 12:1-2, we are sacrificed to God, because we participate in Jesus’ sacrifice. It’s not merely symbolic. We lay our lives on the altar. Because Jesus is the Lamb of God, we become slaughtered lambs as well. We live the Truth.
This is all enabled by the Spirit, who works to transform us so that Truth is not merely what we believe but what we become and how we live. Our faith in Jesus transforms us, by the Spirit, to become like Jesus.
No longer is worship rules or location centered; it’s Christ-centered. Our worship — our sacrifice — is acceptable, not because of the rules but because we are in Christ.
We often miss the point and study incorrectly because we take “worship” to mean “the Sunday morning assembly,” but Jesus uses the word for “worship” that especially refers to sacrificing an animal on the Temple mount. The Jews bowed before God by offering sacrifice — which was only permitted at the Temple.
Therefore, to see what other light the New Testament sheds on the subject, we need to look at the passages dealing with sacrifice in New Testament terms.
(Rom 12:1-2 ESV) I appeal to you therefore, brothers, by the mercies of God, to present your bodies as a living sacrifice, holy and acceptable to God, which is your spiritual worship. 2 Do not be conformed to this world, but be transformed by the renewal of your mind, that by testing you may discern what is the will of God, what is good and acceptable and perfect.
(Eph 5:1-2 ESV) Therefore be imitators of God, as beloved children. 2 And walk in love, as Christ loved us and gave himself up for us, a fragrant offering and sacrifice to God.
(Heb 13:16 ESV) 16 Do not neglect to do good and to share what you have, for such sacrifices are pleasing to God.
What replaces the Temple sacrifices in the New Testament? The commitment of our entire persons to God. A transformed mind and heart. Imitating the love of Jesus. Doing good and sharing with others.
Service. Submission. Sacrifice. Suffering for the sake of Jesus. That’s worship in Spirit and in truth.
And as we read the rest of John’s Gospel, we’ll see that these are the things we are taught. Jesus wasn’t saying, “Obey the rules for how to worship under the New Covenant that are not yet revealed.” He was saying, “Believe in me and follow me by becoming like me.”
Does this mean we have no instructions for the assembly? No, it just means that Jesus was not speaking specifically about the assembly at the well near Sychar in Samaria. He was speaking of the new sacrificial system, the one where we become the sacrifices by imitating the sacrifice of Jesus.
 I can’t resist mentioning this. This line of reasoning was suggested to me by a fellow elder.
There were seven deacons appointed in Acts 6. We know from other passages that the deacons were a plurality in each congregation. But we know of not a single New Testament congregation that had more or less than seven deacons. Since we have clear authority for seven deacons, and no authority for more or less, how do we justify having two or 20 deacons?
Isn’t the example of seven deacons binding? Just as binding as weekly communion, which is mentioned in Acts 20:6-7 as an example and gives the only authority for when communion may be taken? If it’s sin to take communion quarterly, then it’s surely sin to ordain the wrong number of deacons!
Moreover, the practice of the early church was to have only seven deacons! The 15th canon of the Council of Nicea required that churches have exactly seven deacons! This is the same council that adopted the Nicene Creed.
This bit of history surely seals the case beyond all doubt. It was the later, Catholic corruption of the church that led many churches to have too many or too few deacons.
The Reformation did not complete the purification of the church, because the Reformers — their minds clouded by having newly escaped Catholicism — failed to realize the essentiality of the seven-member diaconate.
The Restoration Movement also missed this point, although they came far closer to restoring the New Testament church.
Today, however, we have found the key to being truly the One True Church — seven deacons and only seven deacons.
And if that’s right (and surely the logic is irrefutable), doesn’t that mean that a church with more or less deacons is not scripturally organized? Just as sinful as a church organized with a single pastor? Or holding quarterly communion?
And if that’s right (and surely the logic is irrefutable), doesn’t that mean that any church with the wrong, unauthorized number of deacons lacks an essential “mark of the church” and is therefore not the true church? And that all its members are therefore damned?
Surely, it’s obvious that those who so willfully violate God’s plain and obvious will are false teachers, ought to be marked, and certainly shouldn’t be invited to speak in our lectureships.
These people may have the right heart, but they do not have “the truth.”
I should write a book. Or, at least, a tract.
 There’s an interesting contrast in the Septuagint. Psalm 119 [118 in the LXX] is a long psalm extolling God’s laws. In the Septuagint, God’s laws are repeatedly referred to as “truth” — the same word used by Jesus. See Psa. 119:30, 43, 75, 86, 90, 138, 142, 151, 160.
(Psa 119:142 ESV) Your righteousness is righteous forever, and your law is true [LXX: truth].
If Jesus is “the truth” then Jesus replaces the Law, and there’s a lot of truth to that.