The operative verb Eph 4:3 is τηρέω (téreó) which occurs 71 times in the NT and which BDAG give the following definition:
- to retain in custody, keep watch over, guard, eg, Matt 27:36, 54, Acts 16:23, 12:5, 24:23, 25:4, 21, Matt 28:4
- to cause a state, condition or activity to continue, keep hold reserve, preserve someone or something
- (a) for a definite purpose or suitable time, eg, John 2:10, 12:7, Acts 25:21a, 1 Peter 1:4, 2 Peter 2:4, 9, 17, 3:7, Jude 6b, 13.
- (b) keep, etc, unharmed or undisturbed, eg, John 14:21, 1 John 5:18, 1 Cor 7:37, 1 Thess 6:14, 1 Tim 5:22, 2 Cor 11:9, James 1:27, 1 Thess 5:23, John 17:11f, Jude 21, 1.
- (c) of holding on to something so as not to give it up or lose it, eg, Eph 4:3, 2 Tim 4:7, Rev 16:15, 1 John 5:18, Jude 6a.
- (d) of being protective, eg, John 17:15, Rev 3:10b
- to persist in obedience, keep, observe, fulfill, pay attention to, especially of law and teaching, eg, Matt 23:3, Acts 21:25, 15:5, James 2:10, Matt 28:20, 19:17, John 14:15, 21, 15:10, ab, 1 John 2:3f, 3:22, 24, 5:3, Rev 12:17, 14:12, observe the Sabbath John 9:6, keep the fast Mark 9:7, the word John 8:51, 55, 14:23, 15:20ab, 17:6, 1 John 2:5, Rev 3:8, John 14:24, Rev 22:7, 9, 2:26.
Note that in Eph 4:3, the meaning is 2(c) above.
However, in Eph 4:13 we have a related by different word, καταντάω (katantaó) which, according to BDAG has this definition:
- to get to a geographical destination, come (to), arrive (at), reach, eg, acts 13:51, 16:1, 18:19, 24, 21:7, 25:17, 27:12, 28:13, 20:15.
- to reach a condition or goal, figurative extension of 1 arrive at, attain, meet
- (a) arrive at something, so that one come to possess it, attain (to) something, eg, Eph 4:13, Acts 26:7, Phil 3:11
- (b) The person does not come to something, but something comes to the person, eg, 1 Cor 14:36, 10:11.
Thus, the meaning in Eph 4:13 is 2(a) above.
Unity of ther Spirit
The phrase "Unity of the Spirit" only ever occurs in Eph 4:3 and nowhere else in the NT, where the verse reads (BLB):
being diligent to keep the unity of the Spirit in the bond of peace;
The verb translated "diligent" here is σπουδάζω (spoudazó) to which BDAG give three basic meanings; but the third and last of these is pertinent here:
3. to be especially conscientious in discharging an obligation, be zealous/eager, take pains, make every effort, be conscientious, eg, Gal 2:10, Eph 4:3, 1 Thess 2:17, 2 Tim 2:15, Heb 4:11, 2 Peter 1:10, 15, 3:14.
These references of this verb include being eager for the following things:
- remembering the poor (Gal 2:10)
- keeping the unity of the Spirit (Eph 4:3)
- Paul's eagerness to see people face to face (1 Thess 2:17)
- present ourselves approved by God (2 Tim 2:15)
- to enter God's Sabbath rest (Heb 4:11)
- to make our election sure (2 Peter 1:10)
- Paul's eagerness to have to people remember what they were taught
- to be found by Him in peace, without spot and without blemish (2 Peter 3:14)
Thus, Eph 4:3 clearly teaches us that we must be eager and diligent to keep/maintain the unity of the Spirit, ie, to be motivated and listen to what the Spirit tells and teaches us, John 16:13, etc. Paul discusses this at length in Rom 8 -
4 so that the righteous standard of the law might be fulfilled in us, who do not walk according to the flesh but according to the
Spirit.
5 Those who live according to the flesh set their minds on the things of the flesh; but those who live according to the Spirit
set their minds on the things of the Spirit. 6 The mind of the
flesh is death, but the mind of the Spirit is life and peace, 7
because the mind of the flesh is hostile to God: It does not submit to
God’s law, nor can it do so. 8 Those controlled by the flesh
cannot please God.
9 You, however, are controlled not by the flesh, but by the Spirit, if the Spirit of God lives in you. And if anyone does not
have the Spirit of Christ, he does not belong to Christ. 10 But if
Christ is in you, your body is dead because of sin, yet your spirit is
alive because of righteousness. 11 And if the Spirit of Him who
raised Jesus from the dead is living in you, He who raised Christ
Jesus from the dead will also give life to your mortal bodies through
His Spirit, who lives in you. ...
... 14 For all who are led by the Spirit of God are sons of
God.
Unity of the Faith
Similarly, the phrase "unity of the faith" is unique to Eph 4:13. However, note the difference in its use contrasted with "unity of the Spirit"
- Eph 4:3 - keep/maintain the unity of the Spirit
- Eph 4:13 - until we reach the unity of the faith
Thus, unity of the Spirit is something we have now but unity of the faith and full knowledge of the Son of God is something that will only be attained in the future; ie, something that we strive towards until "perfection" (Eph 1:17) at the consummation of the ages.