In the Gospels it is somewhat common to read a passage where Jesus knows the thoughts of those he is encountering. Intriguingly, one manuscript of Luke 3:16 (D 05, Bezae) reads, επιγωους τα διανοηματα αυτων ειπεν (tr. "Observing their thoughts he said..." ). In light of narrative textual criticism, which values each variant for it's own contribution to our understanding of early Christianity, I am intrigued by this. Did a scribe intend to give John powers similar to those of Jesus? What does this say about how John was remembered? Or, was the scribe just sleepy?
For some context, v. 15 mentions that the people were pondering whether John himself might be the messiah. Usually, if my memory serves me correctly, when Jesus knows the thoughts of others the mood of the narrative is negative: people doubt him, oppose him, etc. So, this may have something to do with how John is presented. Does John despise the crowd's question about his status as a messiah?
Here is the NA 28 juxtaposed with Bezae for Lk. 3:16 for those who are interested:
NA 28: ἀπεκρίνατο λέγων πᾶσιν ὁ Ἰωάννης· ἐγὼ μὲν ὕδατι βαπτίζω ὑμᾶς· ἔρχεται δὲ ὁ ἰσχυρότερός μου, οὗ οὐκ εἰμὶ ἱκανὸς λῦσαι τὸν ἱμάντα τῶν ὑποδημάτων αὐτοῦ· αὐτὸς ὑμᾶς βαπτίσει ἐν πνεύματι ἁγίῳ καὶ πυρί
Bezae: επιγνους τα διανοηματα αυτων ειπεν εγω ϋμας βαπτιζω εν ϋδατι εις μετανοιαν ο δε ερχομενος ϊσχυροτερος μου εστιν ου ουκ ιμι ϊκανος λυσαι τον ϊμαντα του ϋποδηματος αυτος ϋμας βαπτεισει εν πνευματι αγιω και πυρι 
 Codex Bezae Cantabrigiensis: Greek Transcriptions (International Greek New Testament Project (IGNTP), 2012), Lk 3:16.