A number of people have questionned whether temporary hitpoints generated by multiple uses of the same ability count as the same source, and thus would be cumulative. This dilemma usually comes up in the context of Infernal Pact Warlocks or Bostering Strike Paladins. Stacking temporary hp in these contexts is mostly fair, so this confusion is understandable. Clerics on the other hand are downright silly if temporary hp stack.
The trouble comes from sacred flame, starting at mid to high levels and doesn't require a particularly demanding build. Take an 18 wisdom and 14 charisma at first level, and then place extra stat points in these abilities with levelling. At level 20, this cleric can unequip their implement and then target an ally with sacred flame [as it targets one creature]. In response to a hit, that ally takes 1d6+6 damage (23 wisdom), then gains 10 (1/2 level) + 4 (19 charisma) = 14 temporary hp. After the first shot this will always net at least 2 bonus temporary hp, with an average of 5.5 gained per attack. Assuming a six second round, this exploit can net a total of 3300 temporary hp per hour for the clerics allies, without ever placing anyone in danger. Ouch.
A similar trick is possible with two high wisdom, low charisma paladins, but that seems a much more demanding build with less general utility than a Wis/Cha cleric.
The trouble comes from sacred flame, starting at mid to high levels and doesn't require a particularly demanding build. Take an 18 wisdom and 14 charisma at first level, and then place extra stat points in these abilities with levelling. At level 20, this cleric can unequip their implement and then target an ally with sacred flame [as it targets one creature]. In response to a hit, that ally takes 1d6+6 damage (23 wisdom), then gains 10 (1/2 level) + 4 (19 charisma) = 14 temporary hp. After the first shot this will always net at least 2 bonus temporary hp, with an average of 5.5 gained per attack. Assuming a six second round, this exploit can net a total of 3300 temporary hp per hour for the clerics allies, without ever placing anyone in danger. Ouch.
A similar trick is possible with two high wisdom, low charisma paladins, but that seems a much more demanding build with less general utility than a Wis/Cha cleric.