And the Lord spoke to Moses and Aaron, saying:
so that it can be known at what time a thing is clean or unclean.
Speak to the sons of Israel, and say to them: The man who undergoes a flow of seed shall be unclean.
For the Lord God does not fulfill his word, unless he has revealed his secret to his servants the prophets.
Whatever has been touched by something unclean will itself be made unclean. And the soul who touches any of these things shall become unclean until evening."
In many places and in many ways, in past times, God spoke to the fathers through the Prophets;