Time Warp

As a reaction you can choose one willing creature other than yourself within the range of the spell. A creature targeted by this spell adds a 1d4 to their AC or a saving throw, This roll can be made before or after the result of the roll is known, as you warp time around the creature to potentially change the outcome.

At Higher Levels. 

When you cast this spell using a spell slot of 3rd level or higher,  the die rolled increases to 1d6 at 3rd level, and to a maximum of 1d8 at 4th level.