“The blessed and immortal nature knows no trouble itself nor causes trouble to any other, so that it is never constrained by anger or favour. For all such things come about through weakness.”Epicur · Maximele fundamentale · -280 · Maxima 1
Any divine anger or favor would be weakness, not power.
Epicurus attacks the image of gods who get angry or play favorites. If a god were troubled by anger or gratitude, something would be missing from him, and so he would not be perfect. The logic: needing to react to humans implies dependence on them, and a blessed being depends on nothing. The practical consequence is liberating: there are no offended gods to fear, so religious fear is misplaced.
Why it matters Frees anyone living with the fear that a higher power is punishing them for small thoughts or failures.