Basic Rules, pg. 211

Aid

2-level Abjuration

Your spell bolsters your allies with toughness and resolve. Choose up to three creatures within range. Each target's hit point maximum and current hit points increase by 5 for the duration.
At higher levels: When you cast this spell using a spell slot of 3rd level or higher, a target's hit points increase by an additional 5 for each slot level above 2nd.