Tarzan and the Jewels of Opar by Edgar Rice Burroughs

For a moment Werper had stood above the sleeping ape-man, his murderous knife poised for the fatal thrust; but fear stayed his hand. What if the first blow should fail to drive the point to his victim's heart? Werper shuddered in contemplation of the disastrous consequences to himself. Awakened, and even with a few moments of life remaining, the giant could literally tear his assailant to pieces should he choose, and the Belgian had no doubt but that Tarzan would so choose.

Again came the soft sound of padded footsteps in the reeds -- closer this time. Werper abandoned his design. Before him stretched the wide plain and escape. The jewels were in his possession. To remain longer was to risk death at the hands of Tarzan, or the jaws of the hunter creeping ever nearer. Turning, he slunk away through the night, toward the distant forest.