Someone carefully washes your hands, or you wash them yourself at length. The water is often clear, sometimes warm, almost ritual.
The emotional tone
A progressive appeasement. The dreamer feels lighter as the gesture continues.
Symbolic meaning
Washing your hands in a dream is a gesture of purification, symbolic, never trivial. It marks the end of a cycle, the laying down of a burden, the acceptance that you are no longer responsible for what you carried.
The palmistry link
In palmistry, the palm changes slowly with great passages. Dreaming of washing your hand is dreaming of accepting the change, that old lines can fade to let others inscribe themselves.
What this dream signals in your life
This dream arrives at the end of an accepted ordeal. It's rare in those still inside, frequent in those coming out.
Washing your hands in a dream is deciding, somewhere, to no longer have to wash them.