Numbers 19:12
On the third day and on the seventh day he is to make himself clean with the water, and so he will be clean: but if he does not do this on the third day and on the seventh day, he will not be clean.On the third day and on the seventh day he is to make himself clean with the water, and so he will be clean: but if he does not do this on the third day and on the seventh day, he will not be clean.