Counterspell - Return to Sender

You attempt to interrupt a creature in the process of casting a spell with you as the target. If the creature is casting a spell of 3rd level or lower, its spell fails and has no effect. If it is casting a spell of 4th level or higher, make an ability check using your spellcasting ability. The DC equals 10 + the spell's level. On a success, the creature's spell fails and has no effect and as a free action you can redirect the spell back at its sender with your own spell attack modifier if needed. If it is a concentration spell it ends the following round and does not require concentration during that time. 

At Higher Levels. When you cast this spell using a spell slot of 5th level or higher, the interrupted spell has no effect if its level is less than or equal to the level of the spell slot you used and can be redirected as stated above.