Der Mensch kann nicht leben ohne ein dauerndes Vertrauen zu etwas Unzerstörbarem in sich, wobei sowohl das Unzerstörbare als auch das Vertrauen ihm dauernd verborgen bleiben können. Eine der Ausdrucksmöglichkeiten dieses Verborgenbleibens ist der Glaube an einen persönlichen Gott.
Man cannot live without a permanent trust in something indestructable in himself, though both the indestructable element and the trust may remain permanently hidden from him. One of the ways in which this hiddenness can express itself is through faith in a personal god. [Kaiser/Wilkins]
A man cannot live without a steady faith in something indestructable within him, though both the faith and the indestructable thing may remain permanently concealed from him. One of the forms of this concealment is the belief in a personal god. [Hofmann]
Kaiser/Wilkins marks this one cancelled.
What is necessary in order to live, the practical, will be true from a human point of view, but whether or not it amounts to objective truth is not something that can be made to depend on its being necessary.
The word dauernd(es) is used first to express the constancy of belief, and then to express the constancy with which both the object of this faith and the faith itself are concealed. This might remotely imply a common actor in each case, making the belief and its concealment the work of one actor, "man." If not, then one would be doing the believing and another the hiding.
Both translators choose to keep god in the lowercase, although I believe the original wording would justify a capitalized God just as well; the lowercase god would be any god, while uppercase would indicate the God of monotheism.
This aphorism appears to say that man projects what he needs to believe indestructable about himself into another being, perhaps in order to put it out of reach of destruction; this also masks the true nature of the belief. One thinks one believes in God, but really believes in the self. What changes is made to depend on what doesn't change, while depending on change itself is apparently too alarming an idea.
Bergson wrote extensively about this problem, but I have no reason to think Kafka had read Bergson. In brief, Bergson maintained that the self exists solely as a continuous flux, but that it is more practically expedient to ignore this and think of it as fixed; change is understood as a succession of fixed impressions, rather than as a continuous flow, and so the continuity of one moment to the next, past and present, has to be supplied by another means, which is the fiction of the stable self as a kind of stage on which these fixed impressions come and go. The stage is beyond the reach of change, and so it is indestructable.
This is ultimately what is meant by the idea of the soul, and with that idea comes God too. Just as there are fixed impressions succeeding each other on a stage in the soul, so there are fixed souls succeeding each other in the greater unfolding of time, and the "stage" on which that happens is God. God is to the many distinct human souls, from this point of view, what the soul is to the many different fixed impressions of life. Same scheme.
This aphorism doesn't bear directly on the existence of God or even of what is indestructable since it only deals with what people need to believe.