Recovering From Ability Damage
Temporary ability damage heals at the rate of 1 point per night of rest (8 hours) for each affected ability score. Complete bed rest for 24 hours restores 2 points for each affected ability score. Ability drain does not heal naturally. See Ability Damage, Ability Drain, and Negative Levels on page 252 for more information.
Source
Core Rulebook pg. 251