What kind of baptism was Israel's baptism in 1 Corinthians 10 if it wasn't water?
The baptism in 1 Corinthians 10 was not water baptism but a baptism of identification. Israel was placed under Moses' leadership and the Shekinah Glory cloud, passing from Egyptian slavery to freedom as God's set-apart people. It signified their identification with Moses and his leadership.
Les explains that the context is Israel in the wilderness, fresh out of Egypt, not a New Testament church. They passed through the sea, going from slavery under the Egyptians to freedom as the people of God. Their baptism was not water; it was their placement under Moses' leadership and under the Shekinah Glory cloud that accompanied them, and it was called a baptism. Les says this means they were identified with Moses and his leadership. He also notes that definitions matter, since baptism can describe being placed under something, as when Jesus spoke of His coming baptism of suffering, death, burial, and resurrection.
Moreover, brethren, I would not that ye should be ignorant, how that all our fathers were under the cloud, and all passed through the sea;
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