Obligatory Charity Tax (Zakat)

Bukhari :: Book 2 :: Volume 24 :: Hadith 525

Narrated Um 'Atiyya:

A sheep was sent to me (Nusaiba Al-Ansariya) (in charity) and I sent some of it to 'Aisha. The Prophet asked 'Aisha for something to eat. 'Aisha replied that there was nothing except what Nusaiba Al-Ansariya had sent of that sheep. The Prophet said to her, "Bring it as it has reached its place."