"For as the body is one and has many members, but all the members of that one body, being many, are one body, so also is Christ. For by one Spirit we were all baptised into one body — whether Jews or Greeks, whether slaves or free—and have all been made to drink into one Spirit. For in fact the body is not one member but many."

1 Corinthians 12:12-14 (New King James Version)

There is neither Jew nor Greek, there is neither slave nor free, there is neither male nor female; for you are all one in Christ Jesus."

Galatians 3:28 (New King James Version)

Fathers and Saints

* Saint Epiphanius of Cyprus, (4th century), writes, "The Catholic Church, which exists from the ages, is revealed most clearly in the incarnate advent of Christ".
* Saint John of Damascus (676 - 749) observes, "The Holy Catholic Church of God, therefore, is the assembly of the holy Fathers, Patriarchs, Prophets, Apostles, Evangelists, and Martyrs who have been from the very beginning, to whom were added all the nations who believed with one accord".
* According to Saint Gregory the Theologian, (329 - 389) "The Prophets established the Church, the Apostles conjoined it, and the Evangelists set it in order".
* The Church existed from the creation of the Angels, for the Angels came into existence before the creation of the world, and they have always been members of the Church. Saint Clement, (died 102?), Bishop of Rome, says in his second epistle to the Corinthians, the Church "was created before the sun and moon"; and a little further on, "The Church exists not now for the first time, but has been from the beginning".

St. Justin Martyr, (2nd Century), perhaps the first Christian philosopher perhaps widens our understanding of "People of God" to include at least the sages of the one God outside historic Judaism and before Christ.  He suggests some sort of dependence of the philosophers on Moses and the prophets when he writes:-

"And so, too, Plato, when he says, "The blame is his who chooses, and God is blameless," took this from the prophet Moses and uttered it. For Moses is more ancient than all the Greek writers. And whatever both philosophers and poets have said concerning the immortality of the soul, or punishments after death, or contemplation of things heavenly, or doctrines of the like kind, they have received such suggestions from the prophets as have enabled them to understand and interpret these things. And hence there seem to be seeds of truth among all men; but they are charged with not accurately understanding [the truth] when they assert contradictories."    (First Dialogue, Chapter 44).

Perhaps there is also a reference here to the general enlightenment of the Logos that predates the Incarnation, (John 1:9)

Contemporary

"The first followers of Jesus in the "days of His flesh," were not isolated individuals engaged in their private quest for truth. They were Israelites regular members of an established and instituted Community of the "Chosen People" of God ... Indeed; a "Church" already existed when Jesus began His ministry. It was Israel, the People of the Covenant... The existing Covenant was the constant background of His preaching. The Sermon on the Mount was addressed not to an occasional crowd of accidental listeners, but rather to an "inner circle" of those who were already following Jesus . . . "The Little Flock" that the community which Jesus had gathered around Himself was, in fact, the faithful "Remnant" of Israel, a reconstituted People of God. . Each person had to respond individually by an act of personal faith. This personal commitment of faith, however, incorporated the believer into the Community. And this remained forever the pattern of Christian existence: one should believe and confess, and then he is baptized, baptized into the Body."

(Fr. George Florovsky “Worship and Everyday Life: An Eastern Orthodox View,” Studia Patristica, vol. 2 (1963), p. 266.)

Articles

"The People of God: An Orthodox Perspective" by George C. Papademetriou

http://www.goarch.org/en/ourfaith/articles/article9285.asp

Τhe People Of God: Its Unity And Its Glory by Constantine Scouteris

The Father George Florovsky Memorial Lecture.
Α discussion of John 17:17-24 in the light of patristic thought

http://www.myriobiblos.gr/texts/english/scouteris_people_10.html

Exploration

Pascha Cycle - "Repentance"

Pentecost Cycle - "The Church"

Holy Cross Cycle - "Reconciliation"

Nativity Cycle - "Covenant"