Comrades in Arms

You create a bond between up to four willing creatures you can see. All must be within range. For the duration of the spell, a creature may, as a bonus action, transfer any number of its hit points to another creature affected by the spell. Any hit points that would raise a creature over its maximum number of hit points are gained as temporary hit points. Temporary hit points gained through this spell vanish when the spell ends, but other hit point changes are permanent.