First, do no harm. (attributed to the medical Hippocratic oath)

"...if you can, serve other people, other sentient beings. If not, at least refrain from harming them." (attributed to His Holiness the Dalai Lama in "The Art of Happiness," His Holiness the Dalai Lama and Howard C. Cutler, M.D., Riverhead Books, 1998)