From Jimmy on Dragonsfoot.org forums, Classic D&D.
Why not make a regeneration spell?
Level: cleric 2
Duration: 1 minute/level
Effect: Heals 2hp/minute
The target of this spell gains regeneration. 2 health points are healed each minute while this spell operates. Only damage that occurs during the spell can be healed. Damage caused by fire or acid cannot be regenerated. This first 2 points of regeneration occur at the end of the round damage is first taken for the duration of the spell.
(a minute is 6 combat rounds in basic)
adjust as desired to fit your campaign and game balance.