They  have such familiarity
with earth(soil) and earth(soil) is the manifestation  of the 
poverty of  created in front of
creator ; in prayer, the meaning of that ' you place the forehead on the soil'
is the same: You  won't  have any way to the grades of nearness(to
God) until you become familiar with earth(soil).
Martyr Avini:the narrator of holy defence of Iran 
