Mukhtasar Bukhari (Abridged) 738 — Do not take defective animals

Narrated Anas (may Allah be pleased with him): Abu Bakr As-Siddiq (may Allah be pleased with him) wrote a document for him (containing the rulings of Zakat) which Allah had commanded His Messenger (peace and blessings be upon him). (It also contained this statement:) "In Zakat, an old, defective, or male animal should not be taken, i.e., a goat, etc. Unless the one giving charity wishes so." (Then there is no harm in taking a male animal.)