With a full night's rest (8 hours of sleep or more), you recover 1 hit point
per character level. Any significant interruption during your rest prevents you from healing that night.
If you undergo complete bed rest for an entire day and night, you recover twice your character level in hit points
Various abilities and spells can restore hit points
Healing Ability Damage:
is temporary, just as hit point damage
is. Ability damage
returns at the rate of 1 point per night of rest (8 hours) for each affected ability score. Complete bed rest restores 2 points per day (24 hours) for each affected ability score.