Very truly, I tell you, whoever receives one whom I send receives me; and whoever receives me receives him who sent me. (John 13:20)
Whoever receives you receives me, and whoever receives me receives him who sent me. // Whoever listens to you listens to Me; whoever rejects you rejects Me; and whoever rejects Me rejects the One who sent Me.” (Matthew 10:40//Luke 10:16)
And he took a child and put him in the midst of them, and taking him in his arms, he said to them, “Whoever receives one such child in my name receives me, and whoever receives me, receives not me but him who sent me… For truly, I say to you, whoever gives you a cup of water to drink because you belong to Christ will by no means lose his reward. Whoever causes one of these little ones who believe in me to sin, it would be better for him if a great millstone were hung around his neck and he were thrown into the sea.” (Mark 9:36-42, cf. Matthew 18:6-7, Luke 17:1-2)
But Saul was ravaging the church… And falling to the ground, Saul heard a voice saying to him, “Saul, Saul, why are you persecuting me?” And he said, “Who are you, Lord?” And he said, “I am Jesus, whom you are persecuting.” (Acts 8:3, 9:4-5)
And so by your knowledge this weak person is destroyed, the brother for whom Christ died. Thus, sinning against your brothers and wounding their conscience when it is weak, you sin against Christ. (1 Corinthians 8:11-12)
Scholars of the historical Jesus use a number of criteria in order to determine the authenticity of a given saying or event depicted in the Gospels. One such criteria is Independent Attestation. This refers specifically to sayings that are found in multiple independent sources. Independent sources are those that have no literary connection with each other. So, for instance, John and the shared Synoptic material are two independent sources. Likewise, the material unique to Matthew is an independent source, and so on. Based on this criteria the sayings concerning Jesus’ solidarity with his disciples (listed above) represent some of the most primitive Jesus-material available. The idea that how one treats a disciple is how one treats the Messiah appears in almost every layer of Jesus-tradition. Mark, Q, John, Acts, and Paul all reinforce the concept (see also 1 Cor 12:25-27, Didache 4:1, 11:1-5, and Ignatius’ Romans 9:3).
A very similar saying is found in the parable of the Sheep and the Goats, a parable unique to Matthew.
And the King will answer them, “Truly, I say to you, as you did it to one of the least of these my brothers, you did it to me.” (Matthew 25:40)
Does this then represent the Matthean version of the well-attested Jesus-teaching regarding his solidarity with the disciples?
It appears to. As I have argued at length here, in the parable King Jesus judges the nations based upon how they treated his brothers. Whatever was done to the king’s brothers was done to the king. The parable thus dramatizes the solidarity-sayings that are so pervasive in the Jesus-tradition. Those who welcome Christ’s messengers also welcome Christ. Those who reject Christ’s messengers also reject Christ. That such an idea is independently attested by five other early Christian sources makes this interpretation of the parable almost certain.