There was once a pious Jew in one of the villages of late antique Israel who kept a cow to till his fields. Six days a week the cow worked, and on the seventh day she rested. Her master rested too, as the Torah commands in Exodus 20:10 regarding the Sabbath: you shall not do any work, you, your son, your daughter, your male or female servant, your ox, your donkey, or any of your cattle. The cow had never known another rhythm.
Hard times came, and the master was forced to sell her to a neighboring gentile who did not keep Shabbat. The new owner yoked her on a Saturday to plow his field. She stood still. He tugged. She stood still. He whipped her. She stood still. The animal refused absolutely, with the same steadiness with which she had worked six days of every week for her previous master.
The new owner, furious, went back to the pious Jew and demanded to know what was wrong with his cow. The Jew understood immediately. He came out to the field, put his hand on the cow's flank, and whispered in her ear, When you were mine, you rested on Shabbat because I rested. You are no longer mine. Work for this man. The cow, having received permission from the master whose authority she still somehow recognized, lowered her head and pulled the plow.
The new owner was stunned. A beast had better Shabbat observance than he did. He converted to Judaism on the spot and became, according to the tradition, a sage of some reputation known as the ben ha-parah, the Son of the Cow. This exemplum, preserved as number 312 in Moses Gaster's 1924 Exempla of the Rabbis and attributed to Codex Gaster 185, teaches that holiness seeps into everything it touches. Even a cow who has kept Shabbat for years cannot forget it, and her refusal on one Saturday morning can turn a stranger into a brother.