John 1:19-28

19. Καὶ αὕτη ἐστὶν ἡ μαρτυρία τοῦ Ἰωάννου, ὅτε
ἀπέστειλαν οἱ Ἰουδαῖοι ἐξ Ἱεροσολύμων ἱερεῖςκαὶ Λευείτας  ἵνα ἐρωτήσωσιν αὐτόν· σὺ τίς εἶ; 20. καὶ ὡμολόγησεν καὶ οὐκ ἠρνήσατο, καὶὡμολόγησεν ὅτι ἐγὼ οὐκ εἰμὶ ὁ Χριστός. 21. καὶ ἠρώτησαν αὐτόν· τί οὖν; Ἡλείας εἶ; λέγει· οὐκεἰμί. ὁ προφήτης εἶ σύ; καὶ ἀπεκρίθη· οὔ. 
22 .εἶπαν οὖν αὐτῷ· τίς εἶ; ἵνα ἀπόκρισιν δῶμεν τοῖςπέμψασιν ἡμᾶς· τί λέγεις περὶ σεαυτοῦ; 
23. ἔφη· ἐγὼ φωνὴ βοῶντος ἐν τῇ ἐρήμῳ· εὐθύνατε τὴνὁδὸν κυρίου, καθὼς εἶπεν Ἡσαΐας ὁ προφήτης. 24. καὶ ἀπεσταλμένοι ἦσαν ἐκ τῶν Φαρισαίων.25. καὶ ἠρώτησαν αὐτὸν καὶ εἶπαν αὐτῷ· τί οὖν βαπτίζεις, εἰ σὺ οὐκ εἶ ὁ Χριστὸς οὐδὲ Ἡλείας  οὐδὲ ὁ προφήτης; 26. ἀπεκρίθη αὐτοῖς ὁ Ἰωάννης λέγων· ἐγὼ βαπτίζω ἐν ὕδατι· μέσος ὑμῶνστήκει, ὃν ὑμεῖς οὐκ οἴδατε, 27. ὁ ὀπίσω μου ἐρχόμενος, οὗ οὐκ εἰμὶ ἐγὼ ἄξιος ἵνα λύσω αὐτοῦτὸν ἱμάντα τοῦ ὑποδήματος. 28. ταῦτα ἐν Βηθανίᾳ  ἐγένετο πέραν τοῦ Ἰορδάνου, ὅπου ἦνὁ Ἰωάννης βαπτίζων.
Inquiries into the text:
1. Watch for the use of the present tense where a past tense may warrant translation. This is called "historical present". It is used by John and other authors.
2. Levites here are one of only about 3 times in the NT. Brown says they are sometimes referred to as "temple police". 
3. The quote from Isaiah is from the LXX. 
You might want to keep reading your commentary, if you are not. John offers a lot of insight.

John 1:1-5

 

1 Ἐν ἀρχῇ ἦν ὁ λόγος, καὶ ὁ λόγος ἦν  πρὸς τὸν θεόν, 
     καὶ θεὸς ἦν ὁ λόγος.
 2 οὗτος ἦν ἐν ἀρχῇ πρὸς τὸν θεόν.
 3 πάντα δι’ αὐτοῦ ἐγένετο, καὶ χωρὶς
     αὐτοῦ ἐγένετο οὐδὲ ἕν ὃ γέγονεν 
 4 ἐν αὐτῷ ζωὴ ἐστιν, καὶ ἡ ζωὴ ἦν τὸ φῶς τῶν ἀνθρώπων.
 5 καὶ τὸ φῶς ἐν τῇ σκοτίᾳ φαίνει, καὶ ἡ σκοτία αὐτὸ οὐ κατέλαβεν.

Points to ponder: 

1. At the end of verse 3 there is a variant reading in case you are interested. You can find this in your GNT or NA27 at the bottom of the page  of this passage. This is called the apparatus and we will be talking about it from time to time.

2. Translations of the last noun clause in verse one is contested by different faiths (hint: the use of the article is important).