Party Healing Spell is a skill in the Heavenly Light skill tree of the Mage class.

Skill Description: Recover all party member's HP as much as the low level recovery. It can be used only when you're a party member.
Required job: Above Third Job
Required skill(s): High level healing research 2 Lv at least
Required points: 50 points in Heavenly Light
Is requirement for: Healing light
Skill type: Support Skill
Weapon Required: Staff
Attribute: Light
Cool time: 20 Seconds seconds
MP Usage: 50 MP
Target: Instant Activation

Heals all party members within range. It says by as much as low level healing, but in experience, it tends to be more. And with a reasonable cool down, it's not longer limited to extreme emergencies.