Acolyte of Compassion (3.5e Feat)
From D&D Wiki
Acolyte of Compassion [Exalted]
Prerequisite: Heal 9 ranks, Initiate of Compassion
Benefit: As a free action, you can take any amount of Constitution damage. When you next use your lay on hands ability (whether it's from levels in Paladin or the Initiate of Compassion feat), you may treat your Charisma score as equal to your actual Charisma score plus the amount of Constitution damage you took. You cannot take more Constitution damage than you have points in Constitution, and if you take damage equal to your Constitution score, you die at the end of the current round. If you are a paladin, the amount of damage you can heal with your lay on hands ability increases by +1 per character level.