Question: What were God's reasons for declaring some food clean and some unclean, or certain conditions such as childbirth, menstruation, and leprosy unclean?
Lots of reasons have been offered. Perhaps there is symbolism in the choice of animals. The clean animals represented virtues, the unclean vices. Or maybe the unclean animals were the ones that the godless countries around Israel used in their pagan worship. One idea is that the unclean animals and the unclean conditions were psychologically repulsive. Others argue that certain animals, scavengers mostly, and the blood of childbirth and menstruation, and, of course, the diseases of chapter 13, were unclean because they were literally unclean. They were unhealthy and lacked hygiene. But all of a sudden, in Acts 10, God told Peter that he could eat everything, that God had declared all these animals clean. Did they suddenly become healthy, too?
Here's what I think, and I am just speculating here, because honestly, I don't know. There is a similar question that may help. Why did God choose Israel? Why didn't he choose the Egyptians or the Canaanites or some other people group. Certainly, it wasn't because the Israelites were better or healthier or less repulsive than the others. They weren't. God chose them because he is God and he gets to choose. He may have his reasons (he may not), but he does not have to tell us, and he didn't. He simply chose. It may sound arbitrary, but I'm eternally grateful he chose me, and I didn't give him a good reason to, either.
He called his people to be holy. To be holy is to be set apart, to be distinguished from what is common. The declaration of clean and unclean reminded the Israelites that God demands purity through obedience and sacrifice. We obey God, not because it makes sense or is beneficial, but because of who he is, the holy, good, righteous, full of grace, all-loving God of the heavens and the earth.
Holy God, You are good. May my life be holy, set apart for Your purposes. You have made me a saint, righteous because of the work of Your Son. You have filled me with Your Holy Spirit. Work Your salvation through me from the inside out. Take my desires and make them Yours, so that what I do will reflect Your character.
God, I have choices in front of me everyday, clean and unclean. May I discern the difference and choose wisely. May I trust in Your ways and follow closely.