Player > Feats > Sacred Strike
You imbue your weapons with the essence of your deity to strike down opposing forces.
Worship a deity of an alignment within one step of your own.
When you make an attack as a standard action against a creature, your attack is treated as having the same alignment as the deity you worship for the purposes of overcoming damage reduction.
If you change which deity you worship, this feat gives you no benefit until you next gain a character level, and then only if you still meet the prerequisite.