Although the number 3 is the most often quoted, i have heard metaphysicians of various traditions or individual beleif state most commonly either 1, 3 or 10 as the factor by which "what you put out is what you get back", implying that it be foolish to harm others, given the consequent karma.
The Law of One is as ancient as the universes of existence:
It's the law of omnipresence in all life,
and it is the Supreme Law over all laws in all dimensions and densities;
we are all ONE.
All beings,
and everything in existence in any universe exists within and of the Prime Creator,
which is All That Is.
When one is harmed,
all are harmed,
and when one is helped,
everybody is healed.
Hence,
in the name of who i AM,
and i am One with All,
i ask that only that which is the highest good of all concerned happen
here and now and through all time and space.
i give thanks that this is done.
SO BE IT.
It has been noted by myself and other light/love-workers, that the strongest of "our powers", (meaning those which the divine chooses to channel through us), are for the benefit of the all. This, then, is why i prioritize relations in which positive synergy is the focus.