Jesus replied, “believe me, a time is coming when you will worship the Father neither on this mountain nor in Jerusalem.
Yet a time is coming and has now come when the true worshipers will worship the Father in the Spirit and in truth, for they are the kind of worshipers the Father seeks. God is spirit, and his worshipers must worship in the Spirit and in truth.”
J 4:21-24
Then they worshiped him and returned to Jerusalem with great joy.
Lk 24:52
A physical altar is not needed. What is needed is Spirit and truth.
In the Lutheran tradition we remember those who sought to deny the word of God by claiming that since the Spirit is within we do not need anything external to ourselves. Those who, in essence, denied the mediatorship of Jesus Christ. The name for those who said these things had a name: Enthusiasts.
The English word enthusiasm has a very different meaning today, but it's from a Greek word, enthousiasmos, it is literally en (in, within) theos (God) -ism; "the god within me".
That the self has direct and unmediated connection with God, and therefore has no need for anything external to the self--such as God's Word or the Sacraments--in order to access, experience, know, and understand God. The self is the final arbiter of truth, the final arbiter of the Spirit's power and work.
While the Lutheran fathers fought tirelessly against this heresy, it was hardly a new heresy. The devil is rarely clever, he recycles his lies.
In the 2nd century there arose in the region of Phrygia a group who claimed to speak on behalf of the Holy Spirit, their leader, a man by the name of Montanus and his two female companions Prisca and Maximilla were "prophets" who saw themselves as the direct mouthpiece of the Holy Spirit. And they claimed that the old Church era had come to an end, that Christ in founding His Church and giving His word--His Gospel--to be preached was an intermediate stage leading to a greater and more enlightened era of the Holy Spirit which had been inaugurated among this Phrygian sect.
And this group, who came to be known as the Montanists, preached this "New Prophecy", as it was so-called. They were actually quite influential, so influential and seductive were what they said that they even managed to snatch away one of the foremost writers and theologians of the time, Tertullian of Carthage. Tertullian may have, eventually, sobered up and returned to the Church; but it's actually unclear. It's also unclear which of his writings he wrote while under their influence--which is why in spite of Tertullian's great mind and large body of work, all which he wrote carries an air of suspicion over it, and must be read with an extremely large grain of salt.
This is hardly the first time, nor would it be the last, where the devil would scheme to subtly encourage a denial of Christ and His word. The false doctrine of Enthusiasm is an ever-present danger that we might always be vigilant against. It does not always show up as an explicit heresy from a sect of would-be prophets. It can show up, and raise its ugly head anywhere where we begin to lose sight of God's most solemn promise: That Jesus Christ alone is the Way, Truth, and the Life. And thus we can only know God through Christ, and thus where Christ gives Himself there is God, and there the Spirit is at work.
So to worship God in Spirit and in truth is not to turn our gaze inward, as though I am the place of Divine Service; rather the Holy Spirit because He is the Spirit of Truth turns us outward to Christ, "He will testify about Me" (John 15:26).
For what is the Temple of God? It is Jesus Christ (John 2:19-21), and by the grace and power of God the Church is the very Body of Christ (1 Corinthians 12:27), so that each of us is a spiritual stone in the structure which God builds (1 Peter 2:5). And we come together to offer the sacrifice of praise (Hebrews 13:15), but it is Christ who as Great High Priest offers the Perfect Sacrifice (Hebrews 10:10-14)--that Sacrifice which we ourselves partake of on the Altar, His own body and blood (1 Corinthians 1:16-18).
For here is the worship of God in Spirit and in truth: That we have been assembled, though many, as grains of wheat harvested and come together and turned into the one loaf, have by our union together in and with Christ, as His Sacred and Mystical Body, receive from God every good and perfect gift by which is our supersubstantial bread ("ἄρτον ... ἐπιούσιον" Luke 11:3) by which we live day-by-day abiding in Christ by the grace of God and the power of the Spirit who quickens us in Christ, to His perfect life which He has by His resurrection, that we should stand before the Father in His righteousness, by His life alone, which we have received.
He is the Vine, we are the branches.
His flesh is true food, His blood true drink.
Here is the water of life that never runs dry.
He is the Mediator. By Him alone we have access to God, and by Him alone are we children of God, and by Him alone can we stand before the Throne of Grace, confessing our sins, having healing and forgiveness of our sins, and salvation. And thus in Him and by Him alone can we bring, together, spiritual worship, the offering of praise from our lips and by our confession of His name.
-CryptoLutheran