There is no exact equivalent to this exclusive mission to the Jews, that this is unique to Matthew. Jesus sent out these 12 apostles (Τούτους τοὺς δώδεκα ἀπέστειλεν ὁ Ἰησοῦς). He commanded them with specific instructions (παραγγείλας αὐτοῖς λέγων). They were to stay away from the gentiles (Εἰς ὁδὸν ἐθνῶν μὴ ἀπέλθητε). They were not allowed to enter any Samaritan town either (καὶ εἰς πόλιν Σαμαρειτῶν μὴ εἰσέλθητε). Thus, they had to stay away from the gentiles and the Samaritans. Their mission, however, was to go to the lost sheep in the house of Israel (πορεύεσθε δὲ μᾶλλον πρὸς τὰ πρόβατα τὰ ἀπολωλότα οἴκου Ἰσραήλ). They were to go and proclaim that the kingdom of heaven was at hand (πορευόμενοι δὲ κηρύσσετε λέγοντες ὅτι Ἤγγικεν ἡ βασιλεία τῶν οὐρανῶν). This is exactly the same teaching as John the Baptist, word for word, as in chapter 3:2. Matthew had John say that the kingdom of heaven (γὰρ ἡ βασιλεία τῶν οὐρανῶν) was at hand, coming near (ἤγγικεν). Notice that Matthew did not say the kingdom of God, but the kingdom of heaven. In fact, it is in the plural, heavens. This connection of the message of John and Jesus is very strong here in Matthew.
Matthew had another unique comment about and his preaching. He said that from that time on (Ἀπὸ τότε ἤρξατο), Jesus was proclaiming (ὁ Ἰησοῦς κηρύσσειν) the same message as John the Baptist in the preceding chapter, 3:2. It almost seems like Jesus had become a disciple of John. The preaching messages of John the Baptist and Jesus were very simple and exactly the same. They both said that people should repent (λέγειν Μετανοεῖτε). People should turn their lives around, with a profound metanoia, a change of their spirit. Matthew had John and Jesus say that the kingdom of heaven (γὰρ ἡ βασιλεία τῶν οὐρανῶν) was at hand, coming near (ἤγγικεν). Notice that Matthew did not say the kingdom of God, but the kingdom of “heavens.” Perhaps this was due to the Hebrew word for heaven that was both singular and plural. Matthew used this apocalyptic phrase over 30 times. He was the only one of the canonical gospel writers to use this term, “kingdom of heaven.”