After a band of Mexicans discover Sproule and the kid, the band's leader gives them water before regaling them with an allegorical story about a lost lamb:
When the lambs is lost in the mountain, he said. They is cry. Sometime come the mother. Sometime the wolf. He smiled at them and raised the sword and ran it back where it had come from and turned the horse smartly and trotted it through the horses behind him and the men mounted up and followed and soon all were gone.
The kid and Sproule were without water in the desert, so instead of hiding from the Mexicans they remained in the open, hoping for the water they eventually received. They were, however, equally likely to meet a wolf, or one who would do them harm, as a mother lamb, or someone who would help them. The faux threat of the leader raising his sword before sheathing it highlights the seemingly arbitrary choice between mercy or violence which determined whether the kid and Sproule would live or die.
While Sproule died shortly thereafter, the kid would go on to be akin to the allegory's wolf on more then one occasion, dealing out not mercy but unadulterated violence. At the same time, the kid prefers to remain silent for much of the novel, perhaps a consequence of internalizing the lesson of the allegory and refraining from crying out for help, lest the wrong person answer. This allegory also gives the reader an early example of Mexicans acting out of kindness, portraying them in a much more positive light than most of the American characters. This helps create the anti-imperialist, condemning tone of Blood Meridian. While the Mexican characters on occasion practice mercy, such mercy is rare to find amongst the warfaring American characters.