He said to him: ‘My son, reincarnations are of the mystery of ‘grafting’. Like one who grafts a tree with another tree that is not of its type, like those who graft trees one to another. But the principle of (Lev. 27:33)... and if he shall exchange it at all... is that it needs to be ‘holy’ for ‘holy’.
For there is a tree which is from the aspect of impurity, which is evil, and because of that it is stated: (Lev. 27:10) He shall not exchange it, good for bad or bad for good... For this is the mystery, of:xxviiBT Berakhot 7a ‘the righteous-one for whom it is evil, and the wicked-one for whom it is good.’