As soon as an ally is wounded, you spring forward to keep your friend standing.

Encounter   ✦     Healing, Martial
Immediate Reaction      Melee 1

Trigger: You or an ally adjacent to you takes damage.

Target: The character who takes the damage

Effect: The target can spend a healing surge and regains additional hit points equal to your Charisma modifier.

Published in Player's Handbook, page(s) 147, Class Compendium.