Aid is a Abjuration Level 2 found in Baldur's Gate 3.
Class and Race Restrictions
Aid can only be used by the following classes / subclasses: Bard, Cleric, Paladin, Ranger.
Additional information for Aid
When the spell is cast at 3rd Level or higher, the target's maximum health increases by an additional 5 hit points for each spell slots level above 2nd.