It is related by Abdullah bin Masood that the Apostle of God said: “The tears that fall from the eyes of a truthful Believer, out of the fear of the Lord, and, then, roll down his face, however little they are, even of the size of a fly [i.e., just one drop], shall prevent the Fire of Hell from [touching] his face.”
It shows that the face that gets wet, at any time, with tears shed in response to the fear of the Lord will remain protected from the Fire of Hell.
When the happy tidings of protection against the Fire of Hell are given in a Tradition, as a result of performing a virtuous deed, it, generally, means that it is the characteristic attribute of that deed, and God will keep him safe from the infernal Fire who will carry it out provided that he is not guilty of a mortal sin which calls for the punishment of Fire, or if he has ever committed a sin entailing damnation, he has offered sincere repentance for it and resolved not to do it again. It must not be taken for an attempt at explaining away a difficulty but even in our common parlance such a condition is supposed to be implied with a promise or assurance of that kind.
Source: Marif ul Hadith