Yohanes 1:49

1:49 Nathanael answered him, “Rabbi, you are the Son of God; you are the king ¹  of Israel!” ² 

Matius 23:7

23:7 and elaborate greetings ³  in the marketplaces, and to have people call them ‘Rabbi.’

[1:49]  ¹ tn Although βασιλεύς (basileus) lacks the article it is definite due to contextual and syntactical considerations. See ExSyn 263.

[1:49]  ² sn Nathanael’s confession – You are the Son of God; you are the King of Israel – is best understood as a confession of Jesus’ messiahship. It has strong allusions to Ps 2:6-7, a well-known messianic psalm. What Nathanael’s exact understanding was at this point is hard to determine, but “son of God” was a designation for the Davidic king in the OT, and Nathanael parallels it with King of Israel here.

[23:7]  ³ sn There is later Jewish material in the Talmud that spells out such greetings in detail. See H. Windisch, TDNT 1:498.