Latreuō is a Greek verb usually translated either “worship” or “serve.” In the Septuagint (LXX), it’s the verb most commonly used of worship at the tabernacle or Temple. It is also used of worshiping an idol.
(Deu 6:12-15 ESV) 12 then take care lest you forget the LORD, who brought you out of the land of Egypt, out of the house of slavery. 13 It is the LORD your God you shall fear. Him you shall serve and by his name you shall swear. 14 You shall not go after other gods, the gods of the peoples who are around you — 15 for the LORD your God in your midst is a jealous God — lest the anger of the LORD your God be kindled against you, and he destroy you from off the face of the earth!
And so, latreuō takes on the flavor of “be loyal to” or “honor” or even “obey.” The God or god your latreuō is the God or god who commands your allegiance.
(Deu 10:12-13 ESV) “And now, Israel, what does the LORD your God require of you, but to fear the LORD your God, to walk in all his ways, to love him, to serve the LORD your God with all your heart and with all your soul, 13 and to keep the commandments and statutes of the LORD, which I am commanding you today for your good?”
Thus, when Paul says to his shipmates as he was being taken to Rome —
(Act 27:23-24 ESV) 23 For this very night there stood before me an angel of the God to whom I belong and whom I worship, 24 and he said, ‘Do not be afraid, Paul; you must stand before Caesar. And behold, God has granted you all those who sail with you.’
— Paul didn’t mean by “whom I worship” that he attended weekly song services or listened to sermons. He meant that he had given his allegiance to the God of the Jews, and that his life was dedicated to him. He was speaking of the entirety of how he lived his life, not a Sunday morning assembly merely.
Just so, in —
(Rom 1:9-10 ESV) 9 For God is my witness, whom I serve with my spirit in the gospel of his Son, that without ceasing I mention you 10 always in my prayers, asking that somehow by God’s will I may now at last succeed in coming to you.
— Paul has in mind his life as a missionary much more than the Sunday assembly. The parallel with Temple worship is not the assembly but a life devoted to God.
And consider —
(Phi 3:2-6 ESV) Look out for the dogs, look out for the evildoers, look out for those who mutilate the flesh. 3 For we are the circumcision, who worship by the Spirit of God and glory in Christ Jesus and put no confidence in the flesh — 4 though I myself have reason for confidence in the flesh also. If anyone else thinks he has reason for confidence in the flesh, I have more: 5 circumcised on the eighth day, of the people of Israel, of the tribe of Benjamin, a Hebrew of Hebrews; as to the law, a Pharisee; 6 as to zeal, a persecutor of the church; as to righteousness under the law, blameless.
In v. 3, Paul is comparing Christian worship (latreuō) to the worship of God by the Jews at the Temple. His point is that we Christians have the true “glory” (Heb: Shekinah) of God. God’s Glory once dwelled in the Holy of Holies, but the Second Temple never received the presence of God’s Glory as did Solomon’s Temple and the tabernacle before it. God has rejected the Second Temple and place his Shekinah in the church by means of the Spirit.’
When Paul claims that the church is “the circumcision” he is also referring to the Spirit, based on such passages as —
(Deu 30:6 ESV) 6 And the LORD your God will circumcise your heart and the heart of your offspring, so that you will love the LORD your God with all your heart and with all your soul, that you may live.
Hence, the idea of circumcision of the heart by the Spirit replaces physical circumcision and also suggests that the church has become the true Temple where God’s Shekinah dwells in the form of the Spirit.
This makes Christian worship the only true worship because it’s offered in the only true Temple — the body of Christ — which contains the true Holy of Holies in which God dwells by his Spirit — the church.
This is not mere poetry and pretty pictures. In Paul’s mind, this is all quite real. The Spirit really does live within the church. The church really does sacrifice in honor of God in Jesus the Temple, altar, and high priest. The role of the Temple has been completely replaced by a new and better Temple — Jesus of Nazareth, dwelling on earth through his church, his body.