Halakhah for Yoma 77:8

And now after this preface of ours - that the wisdom of God is greater than all wisdom and that He only commands a thing for our good and for our great benefit - we have no difficulty or question in all of the prohibition of foods and distancing of impurity, in everything that the benefit to us is not known and graspable by investigation; as we truthfully know, it is all for the good. And do not wonder, my son, about the matters of impurity, if it is very hidden from every creature - as it is possible that impurity injures the soul and makes it a little sick. And so [too,] have I heard the thing from the mouth of sages. And [it is] similar to that which they, may their memory be blessed, said (Yoma 39a), "'And become impure (nitmeitem) through them' (Leviticus 11:43) - it is written 'and you shall become foolish (nitamtem)'; meaning to say that the springs of the intellect, which is the living soul, is spoiled a little with the matter of impurity.

It is from the roots of the commandment [that it is] because it is known to the Sages that the matter of impurity weakens the power of the intellect and mixes it up and separates between it and the pure and perfect Elevated Understanding. And it will be separated until it is purified. And [it is] as it is written regarding the matter of impurity (Leviticus 11:43), "and do not become impure with them and be impurified (venitmetem) in them" - and they, may their memory be blessed, expounded (Yoma 39a), "and be stupefied (venitamtem) in them"; meaning to say that the the sources of intellect are stupefied by impurity. Hence it is not fitting for a person who is sullied by impurity to be in the holy and pure place, wherein the spirit of God is [found]. And this matter can be compared metaphorically to the palace of a king from which we distance any man that is leprous or disgusting in his body, or even in his clothing. And it is similar to that which is written (Esther 4:2), "for one can not enter the king's gate wearing sackcloth."