The World Federation One Stop Fiqh

Ruling 179

In order to purify the sole of one’s foot or shoe, it is better to walk a distance of fifteen cubits (dhirāʿs)22 or more, even if the impurity is removed by walking less than fifteen cubits or by rubbing the sole of one’s foot or shoe on earth.

22 The length from the elbow to the tip of the middle finger of the hand is known as one dhirāʿ, and it has been said that one dhirāʿ of people of average height is equivalent to approximately 46 centimetres. [Author]