Spare from Evil gives creature you control protection from non-human creatures until the end of the current turn. This means that creatures you control will not be able to receive damage from, be blocked by, or be targeted by the ability of any creature that is non-human.

Most effects that grant a protection ability do so by specifically stating what quality is being protected against; for example, protection from red, protection from artifacts, or protection from Goblins. Spare from Evil is a bit odd in that it grants creatures you control protection from creatures that are not human. In most cases, this is easy to understand, but there is a slight wrinkle.

Creatures that are both human and some other creature type are human. In other words, they are not non-human. For example, if you control a Chapel Geist and have resolved Spare from Evil, it will have protection from non-humans. However, this Chapel Geist can be blocked by an Insectile Aberration. The Aberration in an insect, but it also has the creature subtype of Human and therefore it is not a non-human. This Insectile Aberration will also deal combat damage to the Chapel Geist because of this. Similarly, this Chapel Geist can be targeted by the activated ability of a Daybreak Ranger. The fact that the Ranger is also an Archer and Werewolf does not matter.

When you want to know if something is non-human, you just ask “is it human?” If the answer is “yes,” then it can’t be non-human.