The man who is clean is to sprinkle those who are unclean on the third and seventh days, and on the seventh day he is to purify them. Those who are being cleansed must wash their clothes and bathe with water, and that evening they will be clean. Numbers 19:19
Medical research tells us that the incubation period for most bacteria is within seven days—a fact unknown in Moses’ time. In a primitive culture without antibiotics, bacterial infections could be fatal. These instructions were important so deadly diseases weren’t spread. Furthermore waiting until evening effectively meant waiting until their clothes were completely dry. Pathogenic microbes live in moisture and die with dryness. This is why we have hand dryers in public toilets. Yet God’s people were oblivious to the practical applications of the directions God gave via Moses.
There are other God-given instructions in the Old Testament, particularly regarding the eating of only ‘clean animals.’ Some instructions have hygiene or other medical benefits but not always. Theologians still don’t understand why God instigated some of the laws. Perhaps they had benefits in an ancient culture that archaeologists are yet to discover. Or maybe they were part of Israel being a distinctive people and set apart from other nations. Whatever God’s reasons—and he has his reasons since he acts with purpose—we can take great encouragement from knowing that God’s directions are given for our best interests, even when we don’t understand their purpose.
It builds our faith to remember that God created us and knit us together in our mother’s womb (Psalm 139:13). He knows what’s best for us and acts for our health and well-being, even in the practical matters of life.
A God who pays so much attention to our needs is worthy of our worship.