Whether it is Christian or Buddhist teachings, the universal law of "You reap what you sow" applies. This is what nature teaches us. Whatever seeds we plant, we get the same plant and the same fruit. There is never a mix-up. Similarly, if we want to lengthen our lives, we need to plant the seeds of protecting lives. If the situation is critical, we need to actively save lives.
The universal law is: You reap what you sow. It is so simple! If you plant a bitter melon seed, you will get a bitter melon. You will never get a sweet melon. Yet it never occurs to us that when we work for others, it comes back to ourselves. So every action, every thought we have if it is motivated by love, it brings us fruits of happiness; it brings us health and happinesss. If we cause harm to others, it will come back to harm ourselves. This is just nature's law.