Can Never Be Erased
It is the same as when nine men are waiting to pray. They may be the greatest tzaddikim. But being nine they are still short of the required minyan for prayer. They are forbidden to utter a single word of the communal prayers. All of a sudden some totally insignificant man comes in from the streets. Whoever he may be, he is joined to them. They are ten. Now they can recite the Kedusha. No sooner than they are finished, this same individual makes his escape and goes back to the streets. But the words of holiness which were uttered before can now never be erased.
(Reb Nosson of Breslov)