There are several examples of compassion in The Witch of Blackbird Pond. Hannah Tupper (the "witch" in the story) comforts Kit when she is upset and feeds her cake. She invites Kit into her house and befriends her.
Kit gives private lessons to little Prudence and loans her her hornbook, even though the girl's mother thinks that she cannot learn. Hannah also reaches out to Prudence in friendship.
Nat shows compassion to Hannah by rescuing her when the mob goes after her. He also offers to take Kit away too, but she refuses to leave because her cousin Mercy is very sick with a fever. She does not want to leave Mercy until she is well.
Kit is taken to trial for being a witch. In order to prove her innocence, Nat risks getting in trouble (because he has been banished) by bringing Prudence to the trial to defend Kit.