King James Version

What Does John 17:21 Mean?

John 17:21 in the King James Version says “That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may...” — study this verse from John chapter 17 with commentary, cross-references, and original Greek word analysis.

“That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me.”

John 17:21 · KJV

Faith

Context

19

And for their sakes I sanctify myself, that they also might be sanctified through the truth. sanctified: or, truly sanctified

20

Neither pray I for these alone, but for them also which shall believe on me through their word;

21

That they all may be one; as thou, Father, art in me, and I in thee, that they also may be one in us: that the world may believe that thou hast sent me.

22

And the glory which thou gavest me I have given them; that they may be one, even as we are one:

23

I in them, and thou in me, that they may be made perfect in one; and that the world may know that thou hast sent me, and hast loved them, as thou hast loved me.

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Commentary

KJV Study Commentary
In the High Priestly Prayer, Jesus intercedes for the unity of all believers: 'That they all may be one' (ἵνα πάντες ἓν ὦσιν). This is not organizational or institutional unity but spiritual, relational unity modeled on Trinitarian communion. The pattern is explicitly stated: 'as thou, Father, art in me, and I in thee' (καθὼς σύ, πάτερ, ἐν ἐμοὶ κἀγὼ ἐν σοί). The Father's being 'in' the Son and the Son 'in' the Father describes the mutual indwelling of persons in the Trinity—perichoresis in theological language. Believers are called to participate in this divine unity: 'that they also may be one in us' (ἵνα καὶ αὐτοὶ ἐν ἡμῖν ὦσιν). The phrase 'in us' indicates believers' unity is not merely with each other but participation in the very life of the Triune God through union with Christ and indwelling by the Spirit. The purpose of this unity is missional: 'that the world may believe that thou hast sent me' (ἵνα ὁ κόσμος πιστεύῃ ὅτι σύ με ἀπέστειλας). Christian unity serves as evidence to the watching world that Jesus is the Father's sent one. The verb 'believe' (πιστεύῃ/pisteuē) is in the present subjunctive, suggesting ongoing, continuous belief. When believers manifest supernatural unity—transcending ethnic, social, and cultural divisions—it demonstrates that Jesus is who He claimed to be. Divisions among Christians, conversely, hinder the gospel's advance by contradicting the unity Jesus prayed for and the Trinity exemplifies.

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Historical & Cultural Context

This prayer occurred in the Upper Room (or possibly the Garden of Gethsemane) on the night before Jesus' crucifixion. Having prayed for Himself (John 17:1-5) and for the disciples (17:6-19), Jesus expanded His intercession to include all future believers (17:20-26). The prayer for unity was poignant given the immediate circumstances—within hours, the disciples would abandon Jesus and scatter (Mark 14:27, 50). Peter would deny Him, Thomas would doubt, and rivalries about greatness had surfaced even at the Last Supper (Luke 22:24). Yet Jesus prayed not only for their restoration but for the unity of all who would believe through their apostolic testimony. Early church history demonstrates both the struggle and the power of Christian unity. Acts portrays the Jerusalem church as unified ('they were all with one accord'), crossing socioeconomic barriers (Acts 4:32-37). Yet divisions emerged—between Hebrews and Hellenists (Acts 6), regarding Gentile inclusion (Acts 15), and between Paul and Peter (Galatians 2). The epistles repeatedly call believers to unity (Ephesians 4:3-6, Philippians 2:1-5, 1 Corinthians 1:10). Throughout church history, this verse has been interpreted variously: Roman Catholics citing it for institutional unity under papal authority, Protestants emphasizing spiritual unity in doctrinal essentials, and ecumenical movements using it to pursue organizational mergers. The verse doesn't prescribe specific structures but grounds Christian unity in Trinitarian communion and missional purpose.

Reflection Questions

  1. What does it mean for believers to be 'one' as the Father and Son are one, and how is this different from mere organizational unity?
  2. How does Christian unity (or disunity) serve as evidence to the world about Jesus' identity and mission?
  3. In what ways can believers pursue the unity Jesus prayed for while maintaining commitment to biblical truth?
  4. What is the relationship between union with Christ ('in us') and unity with other believers ('that they all may be one')?

Original Language Analysis

Greek · 27 words
ἵνα1 of 27

“That”

G2443

in order that (denoting the purpose or the result)

πάντες2 of 27

“they all”

G3956

all, any, every, the whole

ἓν3 of 27

“one”

G1520

one

ὦσιν4 of 27

“may be”

G5600

(may, might, can, could, would, should, must, etc.; also with g1487 and its comparative, as well as with other particles) be

καθὼς5 of 27

“as”

G2531

just (or inasmuch) as, that

σύ6 of 27

“thou”

G4771

thou

πάτερ7 of 27

“Father”

G3962

a "father" (literally or figuratively, near or more remote)

ἐν8 of 27

“art in”

G1722

"in," at, (up-)on, by, etc

ἐμοὶ9 of 27

“me”

G1698

to me

κἀγὼ10 of 27

“and I”

G2504

so also the dative case ????? <pronunciation strongs="kam-oy'"/>, and accusative case ???? <pronunciation strongs="kam-eh'"/> and (or also, even, etc.

ἐν11 of 27

“art in”

G1722

"in," at, (up-)on, by, etc

σοί12 of 27

“thee”

G4671

to thee

ἵνα13 of 27

“That”

G2443

in order that (denoting the purpose or the result)

καὶ14 of 27

“also”

G2532

and, also, even, so then, too, etc.; often used in connection (or composition) with other particles or small words

αὐτοὶ15 of 27

“they”

G846

the reflexive pronoun self, used (alone or in the comparative g1438) of the third person, and (with the proper personal pronoun) of the other persons

ἐν16 of 27

“art in”

G1722

"in," at, (up-)on, by, etc

ἡμῖν17 of 27

“us”

G2254

to (or for, with, by) us

ἓν18 of 27

“one”

G1520

one

ὦσιν19 of 27

“may be”

G5600

(may, might, can, could, would, should, must, etc.; also with g1487 and its comparative, as well as with other particles) be

ἵνα20 of 27

“That”

G2443

in order that (denoting the purpose or the result)

ὁ21 of 27
G3588

the (sometimes to be supplied, at others omitted, in english idiom)

κόσμος22 of 27

“the world”

G2889

orderly arrangement, i.e., decoration; by implication, the world (including its inhabitants, literally or figuratively (morally))

πιστεύσῃ23 of 27

“may believe”

G4100

to have faith (in, upon, or with respect to, a person or thing), i.e., credit; by implication, to entrust (especially one's spiritual well-being to ch

ὅτι24 of 27

“that”

G3754

demonstrative, that (sometimes redundant); causative, because

σύ25 of 27

“thou”

G4771

thou

με26 of 27

“me”

G3165

me

ἀπέστειλας27 of 27

“hast sent”

G649

set apart, i.e., (by implication) to send out (properly, on a mission) literally or figuratively

Study Guide

Historical Context

This verse is found in the book of John. Understanding the historical and cultural background helps illuminate its meaning for the original audience and for us today.

Theological Significance

John 17:21 contributes to our understanding of God's character and His relationship with humanity. Consider how this verse connects to the broader themes of Scripture.

Cross-References

Verses related to John 17:21 from Treasury of Scripture Knowledge

1 Corinthians 12:12Colossians 3:11-14John 17:111 Corinthians 12:25-27Philippians 1:27John 13:35

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