Deuteronomy 28:31
Thine ox shall be slain before thine eyes, and thou shalt not eat thereof: thine ass shall be violently taken away from before thy face, and shall not be restored to thee: thy sheep shall be given unto thine enemies, and thou shalt have none to rescue them.
Moses read the curses to all Israel assembled before him from the book he had written, together with the record of their past history and God's promises to them if they would be obedient. The reading set blessing and curse before the people as the outcome of their own course, with obedience bringing the promised good and disobedience bringing the threatened evil.
Disobedience would bring the loss of livestock and other property taken or destroyed before the owners' eyes, with no power to recover them. The owner's ox would be slain before his eyes but he would not eat of it, his ass would be violently taken away from before his face and not restored, and his sheep would be given to enemies with none to rescue them. This was tangible distress in temporal affairs, leaving the people helpless under loss and hardship. Blessings and security depended on obedience, while such seizure and destruction displayed the hardship that follows transgression.
The chapter presents a conditional arrangement in which diligently hearkening to God's voice and doing right and keeping His commandments and statutes brings blessings, security, prosperity, health, holiness, and sheltering preservation, while transgression brings adversity, hardship, loss, and judgment. God's people are visited according to their obedience or transgression, and must choose whether to enjoy the blessings of obedience or suffer the fearful results of transgressing His commands. The Lord sends prosperity for obedience and adversity for transgression. His promises are upon condition of obedience.
Transgressing God's law breaks down the barriers He erected to preserve His people from disease. The slaying of the ox before its owner and the seizure of ass and sheep by enemies pictures the evils, losses, and diseases brought upon human beings because of sin. Obedience would have spared Israel the diseases brought upon Egypt, while God is presented as Healer and Protector of those who keep His covenant. He permits these evils as part of His plan to prove His people and teach obedience, with Christ as invisible leader and mighty Healer, and He alone as Deliverer, Protector, and Healer can relieve and cure them. As He put healing properties into the tree that sweetened the waters of Marah, so He cures the evils of the human heart.
This conditional character explains why the adults of the army that left Egypt were refused entrance into the promised land. Israel's later defeat and loss of the ark show the same principle, that even the ark itself could not protect the people when they disobeyed God's law.