The R&A

Touching sand - when allowed and not allowed

Before making a stroke at your ball in a bunker, you must not:

Deliberately touch sand in the bunker with your hand, a club or rake or any other object to test the condition of the sand and learn information for your next stroke, or
Touch sand in the bunker with your club:
- In the area right in front of or right behind your ball (except as allowed in fairly searching for your ball or in removing a loose impediment or movable obstruction),
- In making a practice swing, or
- In making your backswing for a stroke.

Except in taking actions covered by the bullet points above, the following actions are allowed:

Digging in with your feet to take a stance for a practice swing or the stroke,
Smoothing the bunker to care for the course,
Placing your clubs, equipment or other objects in the bunker (whether by throwing or setting them down),
Measuring, marking, lifting, replacing or taking other actions under a Rule,
Leaning on a club to rest, stay balanced or prevent a fall, or
Striking the sand in frustration or anger.

But you get the general penalty if your actions in touching the sand improve the conditions affecting your stroke. Penalty for Breach of Rule 12.2: General Penalty.

Related Rule - 12.2b