There are three languages in which the Avatar teaches: In
ordinary language, for the masses who follow the shariat
(custom) and ritual of their religion, so that they can
understand;
In language both ordinary and mystical, for the few
advanced souls;
In language wholly mystical, for the circle.
Zarathustra gave the masses shariat, as in those days they
could well understand good thoughts, good words and
good deeds. He did not say in clear words: "Act and don't
care about the result" since they would not have been
able to accept it. So Zarathustra said the same thing, but in
a different way.
Muhammad said: "Keep engrossed in action alone. If you
act well, you will go to heaven; if you act evil, you will go
to hell."
Krishna said: "Act, but do not care for the results.
Dedicate them to me." Why? Because the atmosphere
then was full of warring spirits.
Jesus also said: "Act, but in the spirit of sacrifice."
All these teachings given by the Avatars were according to the exigencies of the times then prevailing.