Cure Light Wounds

Player's Handbook v.3.5 (PH)Core (3.5)
School
Conjuration (Healing)
Casting Time
1 standard action
Components
V, S
Range
Touch
Target
One creature
Duration
Instantaneous
Saving Throw
Will half (harmless) or Will half (see text)
Spell Resistance
Yes (harmless) or Yes (see text)

When laying your hand upon a living creature, you channel positive energy that cures 1d8 points of damage +1 point per caster level (maximum +5).

Since undead are powered by negative energy, this spell deals damage to them instead of curing their wounds. An undead creature can apply spell resistance, and can attempt a Will save to take half damage.