The Greek word ‘ekklesia’ is usually translated as ‘church.’ This word begins with prefix ‘ek’ which means ‘from out of’ and ends with a form of the word ‘kaleo’ which means ‘to call.’ Thus, ‘ekklesia’ means the called ones, or the assembly of those who are called out by God. We get our English word ‘church’ from another Greek word ‘kyriakon.’ We say ‘church’, the Dutch say ‘kirk’, the Scots say ‘kerk’, and the Germans say ‘kirche.’ Within this word is the word ‘kurios’ or ‘Lord.’ That the Church is often spoken of using this word indicates that all those within it belong to the Lord.
Though this is the case, because we live in fallen world and because we ourselves are fallen creatures, the Church doesn’t always reflect what it’s supposed to be. This is why Jesus gives us images to think of the Church like the sheep and the goats and the wheat and the tares. So every time the Church gathers together they gather as a mixed body. Some (hopefully most) are believers while others are not (though they may sincerely think they are). Theologians throughout the history of the Church have spoken of this mixed reality using two terms: the visible and invisible church. By visible they mean those we can see coming and gathering together who make a profession of faith. By invisible they mean those we cannot see who not only profess, but truly possess faith. All men can see the visible church when it gathers together, but only God knows the invisible Church. After warning Timothy of certain false teachers who have come into the church Paul speaks of the invisible Church when he tells Timothy, “But God’s firm foundation stands, bearing this seal: “The Lord knows those who are His…” (2 Tim. 2:19)
This distinction between the visible and invisible is not just a New Testament reality within the Church, it has Old Testament roots as well. Think back to Old Testament Israel. Visible Israel included all those who had the covenant sign of circumcision put on them. This meant that a physical sign was present in the Old Testament to identity the people of God. But, as Paul says in Romans 9:6, not all Israel is truly Israel. Some Israelites who had been circumcised rejected the God of the Israelites. This means within Israel there were those who visibly identified with Israel by their circumcision, as well as those who invisibly identified with Israel by their faith in the God of Israel. This is further clarified for us when Moses speaks of a comparison in Deuteronomy 30:6 referring to a group of Israelites who were circumcised in flesh and circumcised in heart. We know what it means to be circumcised in the flesh, but to be circumcised in heart means that one truly loves God. Who knew the difference between visible Israel and invisible Israel? God did.
This same mixed pattern is not done away with when we cross over into the New Covenant people of God, the Church. Just many unbelieving Israelites had the sign of the covenant placed on them and were mixed in with believing Israelites, so too many unbelievers within the Church today and have partaken of the New Covenant signs (baptism and the Lord’s Supper). All this to say, just as Old Covenant Israel was a mixed body, so too the New Covenant Church is also. But we do not lose heart. Nothing about the Church is invisible to God. While we can only take someone’s word for it, while we cannot look at the true condition of someone’s heart, God “knows those who are His.”
Now we can move on to more about the nature of the Church. It’s a common belief to think the Church began in the book of Acts when the disciples went out to preach and masses of people converted and began gathering together to worship the risen Christ. While there was something new about what was happening in the book of Acts, the Church (or the assembly of God’s people) began long before. Rather than beginning in the book of Acts, the Church extends back all the way to the very beginning. In fact, we could say that wherever we find people worshipping God we also find the Church. Before the fall Adam and Eve were in the very presence of God as He walked in and throughout the garden. After the fall we see Cain and Abel offer sacrifices. Genesis 4:26 mentions that in the days of Seth and Enosh people began to call on the name of the Lord. As Genesis continues we see moments of worship as people build altars, offer sacrifices, and pray calling on God. Fast forward to the Exodus. God redeemed His people out of slavery for what purpose? “…when you have brought the people out of Egypt, you shall worship God on this mountain” (Exodus 3:12) The reason God brought His redeemed people out of slavery in Egypt was for the purpose of worship. Then once God brought them out and brought them to the mountain to worship Him God made them a covenant people, a kingdom of priests, a holy nation distinguished from all other nations in the world.
Peter picks up this same language to describe the New Covenant people of God in 1 Peter 2:9 saying, “You are a chosen race, a royal priesthood, a holy nation, a people for His own possession, that you may proclaim the excellencies of Him who called you out of darkness into His marvelous light.” This type of language is not isolated to Peter alone, much of the same Old Covenant Israelite language is used to describe the New Covenant people throughout the New Testament. That this happens teaches us that Israel and the Church are not two separate peoples with two separate promises from God. No, Israel is continued by and fulfilled in the New Covenant people of God, the Church. So we really can say that the New Covenant Church is true Israel. Paul says as much when he says the true descendants of Abraham are those who believe in the gospel of Jesus Christ (Gal. 3:29). Paul even calls the Galatian believers the ‘Israel of God’ (Gal. 6:16).
Jesus even teaches these very same things Matthew 12:46-50. “While He was still speaking to the people, behold, His mother and His brothers stood outside, asking to speak to Him. But He replied to the man who told Him, ‘Who is My mother, and who are My brothers?’ And stretching out His hand toward His disciples, He said, ‘Here are My mother and My brothers! For whoever does the will of My Father in heaven is My brother and sister and mother.’” G.K. Beale helpfully shows us what is happening in this moment saying, “Here Jesus redefines a true Israelite as ‘whoever does the will of My Father.’ Jesus’s true family consists of those who trust Him, not those who are related to Him by blood. Because Jesus is restoring not only Israel but also all of creation, including Gentiles, the true people of God no longer can be marked out by certain nationalistic badges that distinguish one nation from another. Therefore, in order to become a true Israelite and part of Jesus’s real family, one no longer needs to keep all the specific requirements of Israel’s law that marked Israel out as Israel in contrast to the rest of the nations: laws of circumcision, diet, the temple, the Sabbath, and so on. Jesus is redefining the true Israel, the true people of God, by saying that loyalty to Him is the mark of a faithful Israelite. People no longer must possess the badges of old national Israel in order to be a part of the true, new Israel…You do not have to be of the bloodline of Abraham to be his true child, nor do you have to move to Israel geographically to become an Israelite, you merely have to move to Jesus, true Israel, and embrace Him.”
As I bring this section to a close, let me give you two implications:
First, because the New Covenant Church is now the true Israel and because faith in Christ brings us into that spiritual kingdom we are no longer looking for the current or a future national Israel to be remade. To be looking for that, and to believe in a kind of future geo-political Israel to bring God’s kingdom into this world through a kind of reinstitution of the temple or the Mosaic Law would be a backward move in redemptive history. Paul makes this point in Ephesians 2:11-22 where he describes the two separate people groups of Jew and Gentile. Jews being those who were given the covenants of promise and Gentiles being those who were aliens and strangers to the promises. Paul’s point in this section is that because of the blood of Christ, the two separate peoples become united into one new man. This new man is the Church, the new and true Israel. Anyone, Jew or Gentile, can come into the promises of the covenant if they have faith in Jesus Christ. Again, I’m aware that this view isn’t the majority today, but can you see that the New Testament authors provide us with an inspired interpretation of the Old Testament? According to them, national Israel is no longer the place of promise. Jesus is, and consequently, His Church is too.
Second, the Old Testament belongs to Christians today just as much as it belonged to Israel then. Who is it that Paul uses as an example in Romans 4 to illustrate justification by faith alone in Christ alone that he described in Romans 3? None other than the patriarch Abraham. Where do the plethora of examples of heroic and robust faith found in Hebrews 11 come from? The Old Testament. All the saints of old were justified by faith alone in Christ alone by believing in the promises of God that would one day come to pass in the Messiah. So while we look back at God’s work in Christ, they looked forward to what God would do in Christ. And isn’t it true that all of the promises of God made in the Old Testament come to their ultimate fulfillment in the New Testament? Indeed it is. The Old Testament is a Christian document, or as it is commonly said, “The New is in the Old concealed, and the Old is in the New revealed.”
So what is the Church? “The Church is the people of God in all ages.” The Church is not a building, though buildings are a good thing to build for us to meet in, but people. The Church is also not any people, as if God required nothing to become a child of God, but the covenant people of God throughout all of history.
 R.C. Sproul, Everyone’s a Theologian, page 265.
 R.C. Sproul, Everyone’s a Theologian, page 262.
 G.K. Beale, from Sam Storms, Kingdom Come, page 206-207.
 John Frame, Systematic Theology, page 1019.