Deuteronomy 21:3

Heifer, not above three years old, say the Rabbins. The pagans esteemed those victims more agreeable to the gods, which had not been yoked. Chermon observes, that the Egyptians rejected such as had been once "consecrated to labour." (Grotius) --- This circumstance might here indicate, that the murderer was a son of Belial, or "without yoke;" (chap xiii. 13.; Menochius) and the heifer was slain to shew what he deserved, and must expect if he be discovered. (Haydock)