Deuteronomy 28:61
Also every sickness, and every plague, which is not written in the book of this law, them will the LORD bring upon thee, until thou be destroyed. Also every sickness, and every plague, which is not written in the book of this law, them will the LORD bring upon thee, until thou be destroyed.
The verse belongs to the blessing-and-curse chapters that Moses read to Israel, setting forth plainly the blessings of obedience and the curses of disobedience. Those words were the voice of Christ from the enfolding pillar of cloud, expressing the principles of the law of His kingdom so specifically that minds are not left in ignorance and uncertainty. Its promises are conditional, with obedience bringing blessing and disobedience bringing curse and punishment, so that people must choose whether to enjoy the blessings or suffer the fearful results. They lay a never-ceasing obligation on all whom God has blessed with life and health and temporal and spiritual advantages, with claims just as binding and fresh now as His gifts are fresh and continual, and Christ repeated these directions with His own voice, calling His followers to a life of consecration and self-denial.
It is part of the curse for not observing to do all the words of the law to fear the glorious and fearful name of God, warning that the Lord will bring upon the disobedient every sickness and every plague not written in the book of the law, even beyond those specifically named, until they are destroyed. That destruction comes together with wonderfully great plagues and sore sicknesses of long continuance, and with the diseases of Egypt brought back upon them. It comes with reduction from multitude as the stars of heaven to few in number, with rejoicing to destroy and bring to nought, with plucking from the land, with scattering among all peoples, and with service of wood and stone. It comes with trembling heart and sorrow of mind, with fear day and night without assurance of life, and with return to Egypt in ships to be sold as bondmen and bondwomen.
Disease in the verse is linked to sin and to breaking the protections God established for health and holiness, while obedience to His commandments is the way to live under His care and protection. Disobedience and allowing appetite to rule bring harm, with the weight of the curse growing through successive generations. The chapter is to be read with Deuteronomy 1 to see why the adult army that left Egypt was refused entry into the promised land, because they did not wholly follow the Lord nor do His judgments and keep His ordinances, statutes, and commandments. In Israel's defeat it shows the ark was no automatic protection, for it held the law given at Sinai, and the living God, not the ark, governs prosperity and adversity according to obedience or transgression.