In 9:9-17, Matthew contrasts two types of disciples who are given a choice to follow Jesus, except this time they’re not known merely by their “denomination.” Rather, they’re known by whom they’re willing to eat with.
First, Matthew writes that Jesus was “reclining at table” (ἀνακειμένου). Then he continues, saying that “many tax collectors and sinners” sat and ate next to him, and that Pharisees didn’t like this. After that, the disciples of John the Baptist come to Jesus, asking why his disciples don’t fast as the Pharisees and themselves do. This is especially obvious when compared with Mark and Luke. Through all of this, we aren’t told about any trouble that was raised, but we are told how Jesus responded, and the impression left is that the disciples of John and the Pharisees had come to disrupt table fellowship. They're in Matthew's home not to feast, but to fast, and to question the appropriateness of this great feast. A sign of those who wish to follow Jesus is that they recline at table with him (a theme that returns in chapters 14—16).
According to Matthew, feasting and table-fellowship provides a framework for partnership that promotes peace among “denominational” lines and party lines. If attempts of table fellowship across denominational lines don’t produce peace, then the root of remaining disunity and factions runs much deeper than mere denominational distinctives. A sign of those who don’t wish to follow Jesus is that they disrupt table fellowship and sow seeds of discord among brethren (Prov. 6:19; Rom. 16:17-18). Those who recline at table with Jesus are the peacemakers, and it is they who shall be called sons of God (Matt. 5:9).