Luke 10:16

“He who hears you, hears me; and he who rejects you rejects me; and he who rejects me, rejects him who sent me.”

Jesus then finishes off His condemnations by pointing out to His disciples that they are so much His representatives and one with Him that if people hear them it is as if they hear Him (compare Luke 9:48). But if they reject them then it is as if they reject Him, and not only Him, but also the One Who sent Him. For the Father, the Son and the disciples are one in the work. For the idea of Jesus being ‘sent' see Luke 4:18; Luke 4:43; Luke 9:48. He had a deep sense of being sent by His Father. And they are a part of it. They too are ‘sent'. So they are very much part of God's own planned outreach to the world, and intimately involved in it.

These disciples were thus to see themselves as ambassadors for Christ (2 Corinthians 5:20) and, as such, citizens of Heaven (Philippians 3:20). That is why their names are written in Heaven (Luke 10:20 below).