Zakat (Kitab Al-Zakat)
Dawud :: Book 9 : Hadith 1716
Narrated Al-Mundhir ibn Jarir:
I accompanied Jarir at Bawazij. The shepherd brought the cows. Among them there was a cow that was not one of them. Jarir asked him: What is this? He replied: This was mixed with the cows and we do not know to whom it belongs. Jarir said: Take it out. I heard the Apostle of Allah (peace_be_upon_him) say: No one mixes a stray animal (with his animals) but a man who strays from right path.