Quote 1
"Then be off home as quick as you can," said the Faun, "and – c-can you ever forgive me for what I meant to do?"
"Why, of course I can," said Lucy, shaking him heartily by the hand. "And I do hope you won't get into dreadful trouble on my account." (2.57-58)
Lucy is ready and willing to forgive anyone who is genuinely sorry. Mr. Tumnus feels the need to apologize for a transgression he hasn't even committed!
Quote 2
"Good evening, good evening," said the Faun. "Excuse me – I don't want to be inquisitive – but should I be right in thinking that you are a Daughter of Eve?" (2.2)
Mr. Tumnus understands Lucy's humanity as part of an extended familial relationship stretching back to her Biblical ancestors.
Quote 3
"My old father, now," said Mr. Tumnus, "that's his picture over the mantelpiece. He would never have done a thing like this." (2.35)
We can tell that Mr. Tumnus is trustworthy and good because he has longstanding family values. It's hard to imagine the Witch keeping a portrait of her father above the mantelpiece!