Why were donkeys and similar animals called beasts of burden in Bible times?
In Bible times, donkeys and similar animals were called beasts of burden because they were loaded down with commodities. They carried heavy loads for people, and a burden is something that weighs you down. This literal picture also illustrates how the Law rested heavily on Israel.
Les explains that donkeys and the so forth of ancient times are called beasts of burden because they were loaded down with their commodities. He notes that most people today do not know what it is like to carry a burden—something that just weighs you down. He then connects that literal picture to the Law: the Law was a burden that rested on the shoulders of the people under it. They knew nothing of liberty and nothing except constant fear of it, because if they picked up a stick on the Sabbath day, the result was death—not a slap on the wrist, but death. Before the Faith Way, Israel was under the burden of the Law constantly, 24 hours a day, and was kept shut up under it until the Faith which should afterwards be revealed. Les also emphasizes that Scripture is a progressive revelation: God did not tell everything up front. When He gave the Law, He did not tell Israel and the rest of the world that one day Christ would die and send the world grace. After 1,500 years under the Law, He progressively reveals the tremendous doctrines of grace.