Aid

Source: Player's Handbook

Level 2 Abjuration (Artificer, Bard, Cleric, Druid, Paladin, Ranger)

Casting Time: Action
Range: 30 feet
Components: V, S, M (a strip of white cloth)
Duration: 8 hours

Choose up to three creatures within range. Each target’s Hit Point maximum and current Hit Points increase by 5 for the duration.

Using a Higher-Level Spell Slot. Each target’s Hit Points increase by 5 for each spell slot level above 2.