NOTES for Lev 14:1-32
A leper who had recovered from his disease was prescribed to be purified, as one is purified from sin. More precisely, not from sin itself, but from its consequences; one can only repent of sin, while from the consequences of sin one has to be purified. What does such purification mean? For a pagan, purification means first of all a kind of hygiene, only not physical but psychological and psychosomatic. It was assumed that in the world there is much that can harm a person's psychophysiology if it is allowed to affect human nature.
What was usually considered purifying was something capable of shaking a person up, of acting on body and soul in such a way as to make them undergo a shock, greater or lesser. At the moment of such a shock, a person would, as it were, shake off all stable psychophysical states imposed by external influences, experiencing this as purification and liberation from them. In Yahwism, everything was not quite like that.
Of course, being in God's presence and being sprinkled with sacrificial blood had a stunning effect on human nature, sometimes stunning even in the literal sense. Yet in this case there was something else as well: the effect of God's presence on a person was capable of restoring the psychophysical state that was normal for him and that then allowed him to be sanctified, at the same altar, but through a separate sacrifice.
The consequences of sin, after all, destroyed first of all a person's relationship with God; they destroyed it because they changed his nature, adapting it to sin and to death more than to life, especially life in God's presence. The same thing happened when a person lived for years, even decades, in effect slowly dying, as lepers lived: their nature was transformed, adapting to death instead of adapting to the fullness of life. The rites of purification and the sacrifices were meant to stop this process of adaptation to death and turn it in the opposite direction, as far as such a turn was possible in a world where death reigned.