Ibn Abbas (may Allah be pleased with him) says that the Prophet (peace and blessings be upon him) forbade "confining a living creature (to kill it) and castrating livestock."
Al-Abbas said: No one narrated it except Ubaydullah, and it is regarded as gharib (unusual) from him.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19790
Ubaydullah bin Musa (may Allah have mercy on him) narrated it with his chain, except that he said: "(He forbade) confining a living creature (to kill it); and castrating livestock is a severe confinement."
The Shaykh said: His words 'and castrating livestock is a severe confinement' are an analogy drawn from what was forbidden, namely confining a living creature, and they are the words of al-Zuhri; for others besides Ubaydullah narrated it from Ibn Abi Dhi'b as mursal and made the statement about castration the words of al-Zuhri.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19791
Ibn Abi Dhi'b (may Allah have mercy on him) says: I asked al-Zuhri (may Allah have mercy on him) about castration. He said: Ubaydullah bin Abdullah (may Allah have mercy on him) narrated to me that the Prophet (peace and blessings be upon him) forbade "confining a living creature (to kill it)." Al-Zuhri (may Allah have mercy on him) said: Castration is a severe kind of confinement.
Yunus and Ma'mar likewise narrated it from al-Zuhri as mursal. What is preserved (mahfuz) in this report is what al-Aqadi narrated from Ibn Abi Dhi'b, because Ma'mar and Yunus corroborate it. It has also been narrated on this from another route from Ibn Abbas (may Allah be pleased with him), with a chain that contains weakness.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19792
Ibn Abbas (may Allah be pleased with him) says that the Messenger of Allah (peace and blessings be upon him) said: "There is no castration in Islam, nor laying the foundation of places of worship of the Jews, that is, building them."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19793
Nafi' narrates from Ibn Umar (may Allah be pleased with him) that he disliked castrating livestock and used to say: "Do not make changes in the creation of Allah."
This is the correct version, mawquf (stopping at the Companion), though it has also been narrated as marfu' (attributed to the Prophet).
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19794
Nafi' narrates from Ibn Umar (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) forbade castrating camels, cattle, goats and horses, and said: "The increase of offspring is only through conception."
(b) Ibn Umar (may Allah be pleased with him) narrates from Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) forbade castrating animals and said: "Does the increase of offspring not come through the males?"
(c) Ibrahim bin Muhajir says that Sayyiduna Umar bin al-Khattab (may Allah be pleased with him) wrote to Sa'd (may Allah be pleased with him) that horses should not be castrated and that a horse should not be raced over two hundred.
This wording fits better with the chain through Abdullah bin Nafi', for Abdullah bin Nafi' has a weakness that makes it likely of him to raise mawquf reports (to the Prophet). It has also been narrated from Musa bin Yasar, from Nafi', from Ibn Umar as marfu', but the correct version is mawquf.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19795
Ibn Abbas (may Allah be pleased with him), concerning the saying of Allah Almighty: "And I will surely command them, and they will change the creation of Allah" [Surah al-Nisa: 119], says: "This refers to castrating animals."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19796
Ibrahim (may Allah have mercy on him) says: (It means) the religion of Allah.
Similar to the view of Ibrahim has been related from al-Hasan, Sa'id bin Jubayr and Qatadah.
Bashir (may Allah have mercy on him) says: Umar bin Abd al-Aziz (may Allah have mercy on him) ordered me, during his caliphate, to castrate a mule of his. Al-Hasan (may Allah have mercy on him) was asked about castration and he said: There is no harm in it. Urwah bin al-Zubayr (may Allah have mercy on him) castrated a mule of his.
Ibn Sirin (may Allah have mercy on him) says: There is no harm in castrating horses; if the stallions were left alone, they would devour one another.
Ata' (may Allah have mercy on him) says: There is no harm in castrating an animal whose biting and bad temper are feared.
Following the view of Ibn Umar and Ibn Abbas (may Allah be pleased with them), together with the sunnah narrated on it, is more fitting, and success is from Allah. It may be permissible when a valid purpose is connected with it, as we have related from the Tabi'in.
It is related from the Prophet (peace and blessings be upon him) that "he sacrificed two castrated rams," and their meat is also tastier.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب السبق والرمي / 19798