At the end of Reaver of the South, Guthrum will confront Eivor and suggest that they should listen to wiser heads. At this point you’ll have two dialogue choices:
“I will listen.”
Guthrum provides Eivor with some genuine advice, but he will still leave the camp.
“Do not speak to me that way.”
Guthrum keeps a steady head and provides the same sound advice, leaving the camp immediately after.