We all know that there are quite a few abnormal verses in the Bible, and that there are many odd claims about who will enter "the Kingdom of Heaven." However, this one caught my mind and I felt that it would lead to some interesting and informative discussion.
Deuteronomy 23:1
ESV
"No one whose testicles are crushed or whose male organ is cut off shall enter the assembly of the Lord."
KJV
"He that is wounded in the stones, or hath his privy member cut off, shall not enter into the congregation of the LORD."
Does this really mean what I think it does? Because, if i remember correctly, one of the first recorded uses of Castrati was in 1599 by the Vatican. Wouldn't that mean condemning these boys to hell solely to improve their singing abilities?
You appear to be misreading/interpreting this passage. It actual concerns restrictions on "access to Israels assembly. The national governing body or popular legislature was charged with a broad range of judicial, political, and policy matters (Judg 20.3). The same physiological qualification that the Holiness Collection requires of the priesthood (Lev 21:17-23) now extended to all Israel."
The above is directly quoted from the "New Oxford Annotated Bible New Standard Version".
Actually, I have never heard the interpretation that the New Oxford Annoted Bible NSV makes there. But it doesn't mean castrati, either, not in the sense of the OP.
Traditionally, we have always understood that what this means is that someone with an injury or congenital deformity of the sexual organs making them sterile and/or incontinent is not permitted to serve actively in the priesthood (when there was a Temple standing, or in the days of the Mishkan/tabernacle, of course), nor is such a person allowed to enter into the ritually pure precincts of the Temple or Mishkan [tabernacle].
There have been many hypotheses concerning the meaning or motivation behind this-- it is one of a lengthy list of physical injuries or deformities that restrict one from active service in the Temple priesthood, or from entering the ritually pure precincts of the Temple/Mishkan. The interpretation that has always made the most sense to me is that such injuries, lacking the treatments of modern medicine, when survived in ancient times, could often result in incontinence and/or discharges of fluids from the penis or urethra opening. Urine and all other fluids discharged through the penile opening are ritually impure; as the Temple/Mishkan was always kept in the highest possible state of ritual purity, it would have been inviting disaster to permit into the Temple/Mishkan precincts people who would be likely to render it ritually impure. For the same reason, those suffering death impurity, or recovering from
tzara'at (a kind of skin ailment, often incorrectly translated as "leprosy"), or women bearing menstrual impurity or birth impurity were also not permitted in Temple/Mishkan precincts until they were ritually pure again.