The disciple's attempt to purify the heart is like the person ordered to uproot a tree. However much he reflects and struggles to do so, he is unable. So he says to himself, "I'll wait until I'm more powerful and then uproot it." But the longer he waits and leaves the tree to grow, the larger and stronger it becomes while he only becomes weaker, and its uprooting becomes more difficult.

(Others Sufis Teaching)