Aura of Shielding

You place a protective aura which faintly glints around a creature you can see within range. Once per turn, when the first attack or spell that deals damage against that creature, the creature immediately gains temporary hit points equal to 1d4 + your spellcasting ability modifier before the damage is dealt. On these attacks the caster must make a concentration check or drop the spell, the DC is equal to half the damage dealt to the affected creature. The spell ends if the affected creature falls unconscious.

At Higher Levels. When you cast this spell using a spell slot of 3rd level or higher, the temporary hit points increases by 1d4 for each slot above 2nd level.