Hit, replace, no penalty: rules explained

If your ball hits another player’s ball on the fairway, your ball is played as it lies, and the other player replaces their ball to its original spot with no penalty to either player.

- Brett Brasier

If your ball is played from off the green and hits another ball at rest on the green, there’s no penalty to anyone; you play your ball as it lies, and the other player replaces their ball to its original spot. Penalties only apply if both balls were on the green when the stroke was made from the putting green. You generally drop on the fairway and replace on the green.