Early Christianity had a confusing beginning. It was seen as a sect of Judaism (Acts 24:5; 28:22); but, Jewish religious authorities rejected Jesus as the promised Messiah. Jesus came with priority on the Jews (Matt 15:21-28); but, exposed their neglect of covenantal duty and the insufficiency of their righteousness to enter the Kingdom of God (Matt 21:28-32; 33-45; 22:1-14; Mark 12:1-12; Luke 20:9-19). Early Jewish Believers viewed themselves as the elect of God; but, held that Gentile Believers could not be chosen unless they became Jews and kept the Law (Acts 15:1-35; Gal 2:3-16). Gentile Believers grew arrogant towards the Jews (Rom 11:20-21); but, they weren't recipients of revelation, lacked the covenantal heritage of the Old Testament and were ignorant of the sacrificial system underpinning Jesus' atonement (Rom 11:17-18).

During the first century Rome, Christian Jews worshipped with Orthodox Jews in the synagogues which caused many heated and contentious debates about whether Jesus was the Messiah. The Roman historian Suetonius records, "Since the Jews constantly made disturbances at the instigation of Chrestus, he expelled them from Rome" (Claudius 25:1 – "Chrestus" is likely a reference to "Christus" or "Christ"). Thus in 49 A.D., Roman Emperor Claudius expelled some 40-50,000 Jews from Rome (Acts 18:2).

Against this background, the former rabbi and now apostle to the Gentiles Paul had similar conflicts. Anguished over the disbelief of his fellow Jews, he wrote of identifying with his people and expressed a willingness to sacrifice his relationship with God for their salvation (Rom 9:1-5). Because of God's revelation that Gentile Believers were heirs together with Jewish Believers (Eph 3:3-6; Col 1:26-27), Paul ever concerned with the relationship between believing Jews and Gentiles, wanted to affirm God's election of Gentile Believers.

The apostle Paul uses the terms "kalēo" (Strong's #2564), "klēsis" (Strong's #2821) and "klētos" (Strong's #2821) to express the idea of calling.

"Kalēo" is a verb that expresses the idea of "to call."

"Klēsis" is a noun that expresses the "act of inviting" or "official summons by a recognized authority."

"Klētos" is an adjective that describes the "called ones" or "invited ones."

In most instances, the apostle Paul understands "kalēo" in the context of divine calling. He sees the call of God, as being mediated through the gospel verbally or through the written word of the Bible (2 Thess 2:14-15). Paul speaks of "salvation through sanctification by the Spirit and faith in the truth" as in setting apart (sanctification) for holiness. When Jesus began His ministry, He announced the coming Kingdom of God, "The time is fulfilled, and the Kingdom of God is at hand; repent and believe in the gospel" (Mark 1:15; Matt 3:2; 4:17). The Kingdom of God is only for those who are holy which requires salvation through Christ. To enter the Kingdom, one must be made holy; one must be "reborn" (John 3:1-21).

In his letter to Believers in Rome and Corinth, Paul addresses them as "called ones" with the adjective "klētos" (Rom 1:6; 8:28; 1 Cor 1:24). And in two instances, Paul addresses the Believers as "called as saints" (Rom 1:7; 1 Cor 1:2).

The use of "klētos" in Romans 8:28 is significant, "and we know that God causes all things to work together for good to those who love God, to those who are called (klētos) according to His purpose."

Paul's use of "kletos" is synonymous with "the elect" ("eklektos" in Rom 8:33), those who are obedient to Him become the chosen (Ex 19:4-5; 1 Pet 2:9). Whether Jewish or Gentile Christian, both serve as "called ones" for a divine purpose.

Jewish Christians. In Paul's sorrow of Israel's abject spiritual state, he states their privileges of divine election. They are people of the covenant: recipients of adoption as God's sons, divine glory, the covenants, the Law of Moses, priesthood and Messianic promise (Rom 9:1-4).

For his faith, God made a unilateral and unconditional covenant with Abraham and promised land, a nation and a conduit for blessings to all on earth (Gen 12:1-3).

God elaborates on His promise of a nation to Abraham in His conditional Mosaic Covenant to make the nation of Israel His own possession, a kingdom of priests and a holy nation on earth if they "obeyed His voice and kept His commandments (Ex 19:3-6; Deut 7:6-11).

A further elaboration takes place with a unilateral and unconditional promise to David that his descendant will be established in God's temple and kingdom forever (2 Sam 7:12-17); the Messiah is implied.

The divine purpose of the Jews is to serve as God's holy people and the means of blessing to the world (Romans 9:7-8). Out of the Jews came Jesus Christ the Messiah and High Priest (Heb 4:14-16; 5:1-10).

Gentile Christians. Paul cited Old Testament references to show that God intended to extend mercy to Gentiles and that God's sovereign election was not limited to those of Jewish ancestry (Rom 9:24-26; 10:18-21; 11:11-15).

When Hosea and Isaiah spoke during the apostasy of the divided kingdoms (during the reigns of Uzziah, Jotham, Ahaz and Hezekiah of Judah and Jereboam of Israel), God disclaimed the Jews as His people; however, their prophecies spoke of the future restoration of covenant relationship with a united nation of Israel and God. Paul draws a parallel of the believing Jewish remnant to include the Gentiles, and in so doing, emphasize a contrast of the Gentiles' righteousness by faith verses the Jews' failure in their pursuit of works (Rom 9:24-26; Hos 1:10; Isa 10:22).

Biblical faith requires knowledge of the gospel and a trusting belief in the fact of Jesus the Messiah. Paul confronts the Jews for their failure to accept the gospel and recognize the Savior which was the source of their lack of understanding. In response to their hard heartedness, Paul refers to how God's will react to this form of idolatry by provoking Israel's jealousy (Rom 10:19; Deut 32:21) in making Himself available to the Gentiles in a manner so that their response to the gospel will surpass the Jews (Rom 10:20; Isa 65:1). The Gentiles, who lacked special revelation and religious training, will be more responsive than God's chosen people (Rom 10:17-21).

The divine purpose of the Gentiles is to serve as God's holy people and as an instrument to increase the number of Jewish Believers (Rom 11:11-15).

Called as "saints" which means "holy ones", both believing Jews and Gentiles form a "royal priesthood," a "holy nation" and a "people of God" (1 Pet 2:9-10) who serve as messengers of divine calling to the world (Matt 28:18-20; Mark 16:15-18) mediated through the gospel.

Throughout his epistles, Paul writes to Believers with the hindsight of initial salvation. Paul, former Rabbi and apostle to the Gentiles, is concerned about the relations between Jewish and Gentile Believers and teaching Gentiles about what life as a holy person should look like (Rom 1:5).

With the use of the feminine noun "klēsis," Paul conveys a meaning of "the invitation."

In response to Gentile Believers' arrogance for their faith in light of the Jews lack of, Paul states, with the Abrahamic Covenant in mind, that the invitation of Israel to a unique place in God's unfolding plan of the Kingdom is irrevocable.

"for the gifts and the calling (klēsis) of God are irrevocable." (Rom 11:29)

Speaking towards both Jewish and Gentile Believers, Paul mentions their circumstances under which God made His invitation to them to be a holy people; it was not based on merit.

"For consider your calling (klēsis), brethren, that there were not many wise according to the flesh, not many mighty, not many noble;" (1 Cor 1:26)

God didn't call them for their philosophy, wisdom, political power or upper class status.

Regardless of one's socioeconomic status, God's invitation to be a holy person is to serve as a means to share the gospel, keeping the commandments of God (1 Cor 7:16-24) and be an instrument for His purposes.

"Each man must remain in that condition in which he was called" (klēsis)." (1 Cor 7:20)

"who has saved us and called (klēsis) us with a holy calling, not according to our works, but according to His own purpose and grace which was granted us in Christ Jesus from all eternity," (2 Tim 1:9)

With His crucifixion, Jesus inherits the throne of David and the Kingdom of God with its saints, and Believers become citizens and beneficiaries of the Kingdom's glory. This unseen Kingdom and fulfillment of God's promises is the hope of the invitation.

"I pray that the eyes of your heart may be enlightened, so that you will know what is the hope of His calling (klēsis), what are the riches of the glory of His inheritance in the saints," (Eph 1:18)

Paul exhorts Believers to be worthy of their invitation to holiness and describes some characteristics of a holy people. The pursuit of holiness is long and requires endurance.

With an understanding of how Paul uses the adjective and noun forms of "kalēo," his use of the verb in the sense of a divine call can be better understood.

Paul used "kalēo" in the context of a divine designation of an office (Acts 9:15-16).

"For I am the least of the apostles, and not fit to be called (kalēo) an apostle, because I persecuted the church of God." (1 Cor 15:9)

Paul's low view of himself was in view of his prior life as Saul the persecutor of Jews (Acts 8:1-3).

"But when God, who had set me apart even from my mother's womb and called (kalēo) me through His grace, was pleased" (Gal 1:15).

Paul used "kalēo" in the context of a divine summoning of life.

"(as it is written, "A FATHER OF MANY NATIONS HAVE I MADE YOU") in the presence of Him whom he believed, even God, who gives life to the dead and calls (kalēo) into being that which does not exist." (Rom 4:17)

Some commentators view this verse as pronouncing a sinner righteous; however, the passage instead speaks to Abraham and Sarah's inability to have an offspring and God's promise of a son (Isaac) before he was born (Rom 4:17-20).

Paul used "kalēo" in the context of defining who God chose as His holy people of Israel and illustrated God's sovereignty.

"nor are they all children because they are Abraham's descendants, but: ‘THROUGH ISAAC YOUR DESCENDANTS WILL BE NAMED (kalēo).'" (Rom 9:7)

Romans 9:6 mentions, "not all Israel is descended from Israel" which is understood to mean that "not all of the holy people of Israel is a descendant of Jacob (Israel). Likewise, the holy people of Israel did not include all of Abraham's descendants.

"for though the twins were not yet born and had not done anything good or bad, so that God's purpose according to His choice would stand, not because of works but because of Him who calls (kalēo)," (Rom 9:11)

God chose who would represent His holy line and carry His seed.

Paul used "kalēo" in the context of affirming God's election of holy people.

"and these whom He predestined, He also called (kalēo); and these whom He called (kalēo), He also justified; and these whom He justified, He also glorified." (Rom 8:30)

With Jesus' conclusion of the Parable of the Wedding (Matt 22:1-14) in mind, "For many are called, but few are chosen" (Matt 22:14), Paul is clearly speaking to Believers. It is an affirmation of the election, ultimate completion and security of the salvation process that holy people of God will experience equally whether Jewish or Gentile Believer.

Paul used "kalēo" in the context of reminding Believers of their obligation as holy people.

Paul's teaching about the call of God makes an important connection to Christian ethics. In essence:

You are called to be God's holy people.

Holy people are predestined to be conformed to the image of Jesus.

Therefore behave like Him!

Make your calling and election sure by having a trusting belief in the gospel (2 Pet 1:10).

The connection justifies the obligation of Believers to Christian ethics. Christian ethics is not voluntary (nor coercive). It is behavior pleasing to God and expected of His holy people. And faith which validates one as a holy person is not a work of merit (Rom 4:5); it is the belief in the meritorious work of Jesus.