Is it permissible to castrate a man and dedicate him to the Haram, and has such an act occurred in Islamic history?

Castration of a human being is forbidden by consensus (ijma'), whether the person is young or old, due to the torment it inflicts upon the soul, the disfigurement and danger to life it entails, the nullification of masculinity, the alteration of Allah's creation, and ingratitude for His bounty. The prohibition of castration has been reported in the Prophetic Sunnah, as Ibn Mas'ud said: "We used to raid with the Messenger of Allah (peace be upon him) and we had nothing, so we said: 'Should we not castrate ourselves?' But he forbade us from doing that." The wisdom behind its prohibition is its contradiction to the Legislator's (Allah's) objective of increasing progeny. Therefore, undertaking it is forbidden, regardless of the motivations.