Tarzan, Lord of the Jungle by Edgar Rice Burroughs

Within the dark interior of the beyt Stimbol could see nothing. Just before him he heard a man breathing heavily as might one in a troubled sleep. The would-be murderer paused to steady his nerves. Then, on hands and knees, he crept forward inch by inch.

Presently one of his hands touched the prostrate figure of the sleeper. Lightly, cautiously, Stimbol groped until he had definitely discovered the position in which his victim lay. In one hand, ready, he grasped the keen knife. He scarce dared breathe for fear he might awaken the ape-man. He prayed that Tarzan was a sound sleeper, and he prayed that the first blow of his weapon would reach that savage heart.