Ἀγαπητοί, εἰ οὕτως ὁ Θεὸς ἠγάπησεν ἡμᾶς, καὶ ἡμεῖς ὀφείλομεν ἀλλήλους ἀγαπᾶν.

Ἀγαπητοί, μὴ παντὶ πνεύματι πιστεύετε, ἀλλὰ δοκιμάζε τὰ πνεύματα εἰ ἐκ τοῦ Θεοῦ ἐστιν, ὅτι πολλοὶ ψευδοπροφῆται ἐξεληλύθασιν εἰς τὸν κόσμον.ἐν τούτῳ γινώσκετε τὸ πνεῦμα τοῦ Θεοῦ· πᾶν πνεῦμα ὃ ὁμολογεῖ Ἰησοῦν Χριστὸν ἐν σαρκὶ ἐληλυθότα, ἐκ τοῦ Θεοῦ ἐστι· καὶ πᾶν πνεῦμα ὃ μὴ ὁμολογεῖ τὸν Ἰησοῦν Χριστὸν ἐν σαρκὶ ἐληλυθότα, ἐκ τοῦ Θεοῦ οὐκ ἔστι· καὶ τοῦτό ἐστι τὸ τοῦ ἀντιχρίστου, ὃ ἀκηκόατε ὅτι ἔρχεται, καὶ νῦν ἐν τῷ κόσμῳ ἐστὶν ἤδη.Ὑμεῖς ἐκ τοῦ Θεοῦ ἐστε, τεκνία, καὶ νενικήκατε αὐτούς, ὅτι μείζων ἐστὶν ὁ ἐν ὑμῖν ἢ ὁ ἐν τῷ κόσμῳ.αὐτοὶ ἐκ τοῦ κόσμου εἰσί· διὰ τοῦτο ἐκ τοῦ κόσμου λαλοῦσι καὶ ὁ κόσμος αὐτῶν ἀκούει. ἡμεῖς ἐκ τοῦ Θεοῦ ἐσμεν· ὁ γινώσκων τὸν Θεὸν ἀκούει ἡμῶν. ὃς οὐκ ἔστιν ἐκ τοῦ Θεοῦ οὐκ ἀκούει ἡμῶν. ἐκ τούτου γινώσκομεν τὸ πνεῦμα τῆς ἀληθείας καὶ τὸ πνεῦμα τῆς πλάνης. Ἀγαπητοί, ἀγαπῶμεν ἀλλήλους, ὅτι ἡ ἀγάπη ἐκ τοῦ Θεοῦ ἐστι, καὶ πᾶς ὁ ἀγαπῶν ἐκ τοῦ Θεοῦ γεγέννηται καὶ γινώσκει τὸν Θεόν. ὁ μὴ ἀγαπῶν οὐκ ἔγνω τὸν Θεόν, ὅτι ὁ Θεὸς ἀγάπη ἐστίν. ἐν τούτῳ ἐφανερώθη ἡ ἀγάπη τοῦ Θεοῦ ἐν ἡμῖν, ὅτι τὸν υἱὸν αὐτοῦ τὸν μονογενῆ ἀπέσταλκεν ὁ Θεὸς εἰς τὸν κόσμον ἵνα ζήσωμεν δι' αὐτοῦ. ἐν τούτῳ ἐστὶν ἡ ἀγάπη, οὐχ ὅτι ἡμεῖς ἠγαπήσαμεν τὸν Θεόν, ἀλλ' ὅτι αὐτὸς ἠγάπησεν ἡμᾶς καὶ ἀπέστειλε τὸν υἱὸν αὐτοῦ ἱλασμὸν περὶ τῶν ἁμαρτιῶν ἡμῶν.

Ἀγαπητοί, εἰ οὕτως ὁ Θεὸς ἠγάπησεν ἡμᾶς, καὶ ἡμεῖς ὀφείλομεν ἀλλήλους ἀγαπᾶν.

Θεὸν οὐδεὶς πώποτε τεθέαται·ἐὰν ἀγαπῶμεν ἀλλήλους, ὁ Θεὸς ἐν ἡμῖν μένει καὶ ἡ ἀγάπη αὐτοῦ τετελειωμένη ἐστὶν ἐν ἡμῖν. ἐν τούτῳ γινώσκομεν ὅτι ἐν αὐτῷ μένομεν καὶ αὐτὸς ἐν ἡμῖν, ὅτι ἐκ τοῦ Πνεύματος αὐτοῦ δέδωκεν ἡμῖν.Καὶ ἡμεῖς τεθεάμεθα καὶ μαρτυροῦμεν ὅτι ὁ πατὴρ ἀπέσταλκε τὸν υἱὸν σωτῆρα τοῦ κόσμου. ὃς ἂν ὁμολογήσῃ ὅτι Ἰησοῦς ἐστιν ὁ υἱὸς τοῦ Θεοῦ, ὁ Θεὸς ἐν αὐτῷ μένει καὶ αὐτὸς ἐν τῷ Θεῷ. καὶ ἡμεῖς ἐγνώκαμεν καὶ πεπιστεύκαμεν τὴν ἀγάπην ἣν ἔχει ὁ Θεὸς ἐν ἡμῖν.Ὁ Θεὸς ἀγάπη ἐστί, καὶ ὁ μένων ἐν τῇ ἀγάπῃ ἐν τῷ Θεῷ μένει καὶ ὁ Θεὸς ἐν αὐτῷ.Ἐν τούτῳ τετελείωται ἡ ἀγάπη μεθ' ἡμῶν, ἵνα παρρησίαν ἔχωμεν ἐν τῇ ἡμέρᾳ τῆς κρίσεως, ὅτι καθὼς ἐκεῖνός ἐστι, καὶ ἡμεῖς ἐσμεν ἐν τῷ κόσμῳ τούτῳ. φόβος οὐκ ἔστιν ἐν τῇ ἀγάπῃ, ἀλλ' ἡ τελεία ἀγάπη ἔξω βάλλει τὸν φόβον, ὅτι ὁ φόβος κόλασιν ἔχει, ὁ δὲ φοβούμενος οὐ τετελείωται ἐν τῇ ἀγάπῃ. 

Ἡμεῖς ἀγαπῶμεν αὐτόν, ὅτι αὐτὸς πρῶτος ἠγάπησεν ἡμᾶς.ἐάν τις εἴπῃ ὅτι ἀγαπῶ τὸν Θεόν, καὶ τὸν ἀδελφὸν αὐτοῦ μισῇ, ψεύστης ἐστίν· ὁ γὰρ μὴ ἀγαπῶν τὸν ἀδελφὸν ὃν ἑώρακε, τὸν Θεὸν ὃν οὐχ ἑώρακε πῶς δύναται ἀγαπᾶν;καὶ ταύτην τὴν ἐντολὴν ἔχομεν ἀπ' αὐτοῦ,ἵνα ὁ ἀγαπῶν τὸν Θεὸν ἀγαπᾷ καὶ τὸν ἀδελφὸν αὐτοῦ.

(πηγή:Καθολική Επιστολή Α Ιωάννου,4)