Originally posted by Richard Harnack
I think you will find it in his "rules" in Budo.
In the English translation which I have in front of me, the first "precaution for training" says this:
"The original intent of bujutsu was to kill a enemy with one blow; since all techniques can be lethal, observe the instructor's directions and do not engage in contests of strength."
I don't think that's really addressing the issue of competition per se so much as attitude on the mats, although you could certainly extrapulate from the statement.