Why did Mr beaver not want the children to save Mr tummus?

Mr. Beaver was initially hesitant to let the children save Mr. Tumnus because he feared that doing so would put them all in danger. He understood that rescuing Tumnus from the White Witch could provoke her wrath, potentially leading to dire consequences for the children and their mission in Narnia. Mr. Beaver's protective instincts were focused on ensuring the children's safety and the success of their quest to defeat the Witch.