First, the author places μὴ μένων (“does not abide”) in antithesis to ὁ παραβαίνων (“transgresses”). We could simplify the statement by removing one of the elements of the antithesis, thus producing the following:
9 Whoever does not abide in the doctrine of Christ does not have God. He who abides in the doctrine of Christ has both the Father and the Son.
To abide in the doctrine (teaching) of Christ is to abide in Christ’s words.1 “To abide in” Christ’s doctrine and words would be equivalent to “to abide by” Christ’s doctrine and words. According to LSJ, one use of μένω is:2
According to Oxford English Dictionary, to “abide by” means:3
To abide by means to submit to, obey, and act (walk) in accordance with Christ’s doctrine and words.
In Protagoras, Plato wrote,4
and by showing us the truth would have brought our soul into the repose of abiding by the truth, and so would have saved our life. Would men acknowledge, in view of all this, that the art which saves our life is measurement, or some other?
δὲ τὸ ἀληθὲς ἡσυχίαν ἂν ἐποίησεν ἔχειν τὴν ψυχὴν μένουσαν ἐπὶ τῷ ἀληθεῖ καὶ ἔσωσεν ἂν τὸν βίον; ἆρ᾽ ἂν ὁμολογοῖεν οἱ ἄνθρωποι πρὸς ταῦτα ἡμᾶς τὴν μετρητικὴν σῴζειν ἂν τέχνην ἢ ἄλλην;
Now, in John 14:23, the Lord Jesus Christ said,
23 Jesus answered and said to him, “If anyone loves Me, he will keep My word; and My Father will love him, and We will come to him and make Our home with him. NKJV, ©1982
ΙΓʹ ἀπεκρίθη ὁ Ἰησοῦς καὶ εἶπεν αὐτῷ Ἐάν τις ἀγαπᾷ με τὸν λόγον μου τηρήσει καὶ ὁ πατήρ μου ἀγαπήσει αὐτόν καὶ πρὸς αὐτὸν ἐλευσόμεθα καὶ μονὴν παρ᾽ αὐτῷ ποιησόμεν TR, 1550
The Greek word translated into English as “home” is the noun μονὴν, declined from μονή, which is the noun related to the verb μένω.
Thus, whoever abides by Christ’s doctrine (his words), he has both the Father and the Son, because the Father and Son dwell in that person, and that person, in turn, dwells in the Father and the Son. This is accomplished by means of the Holy Spirit.
In 1 John 3:23–24, it is written,
23 And this is His commandment: that we should believe on the name of His Son Jesus Christ and love one another, as He gave us commandment. 24 Now he who keeps His commandments abides in Him, and He in him. And by this we know that He abides in us, by the Spirit whom He has given us. NKJV, ©1982
ΚΓʹ καὶ αὕτη ἐστὶν ἡ ἐντολὴ αὐτοῦ ἵνα πιστεύσωμεν τῷ ὀνόματι τοῦ υἱοῦ αὐτοῦ Ἰησοῦ Χριστοῦ καὶ ἀγαπῶμεν ἀλλήλους καθὼς ἔδωκεν ἐντολὴν ἡμῖν ΚΔʹ καὶ ὁ τηρῶν τὰς ἐντολὰς αὐτοῦ ἐν αὐτῷ μένει καὶ αὐτὸς ἐν αὐτῷ καὶ ἐν τούτῳ γινώσκομεν ὅτι μένει ἐν ἡμῖν ἐκ τοῦ πνεύματος οὗ ἡμῖν ἔδωκεν TR, 1550
1 John 8:31
2 LSJ, p. 1103, μένω, 6.
3 OED, “abide” (v.), 14.
4 Plato, Protagoras, §356e
Liddell, Henry George; Scott, Robert; et al. A Greek-English Lexicon. 9th ed. with revised supplement. Oxford: Clarendon, 1996.
Oxford English Dictionary (online).
Plato. Plato in Twelve Volumes. Trans. Lamb, W. R. M. Vol. 3. Cambridge: Harvard UP, 1967.
Plato. Platonis Opera. Ed. Burnet, John. Vol. 3. Oxford: Clarendon, 1903.