For whoever is ashamed of me and of my words in this adulterous and sinful generation, of him will the Son of Man also be ashamed when he comes in the glory of his Father with the holy angels.”” (Mark 8:38, ESV)

A couple of things that Jesus says here:

  1. The Son of Man [Jesus] will come “in the glory of his Father and with the holy angels.” – The disciples did not understand what Jesus meant yet, it would not be until the resurrection that they began to have an inkling, and not until Jesus departed that they would begin to fully understand that Jesus had promised to return for them.  Here is a promise and prophecy of Christ’s second coming.
  2. Shame of Jesus and his words in this life leads to unthinkable consequences in the life to come. If we are ashamed of Jesus in this life, then he will be ashamed [will reject] us when he comes for his followers.  This is not a proclamation of salvation by works, but a declaration that true disciples of Jesus will gladly admit and demonstrate by their lives that they are his disciples.

The Zondervan NIV Study Bible comments here: “The world’s standards have no place in God’s kingdom, and Jesus will repudiate those who hold them.”