Hadith 720:2
Aswad ibn Amir narrated to us, Zuhayr narrated to us, from al-A’mash, from Ya’qub ibn Buhayr, a man from the tribe, who said: I heard Dirar ibn al-Azwar say: We gifted a milch camel to the Messenger of Allah, may Allah bless him and grant him peace. He said: So I milked it. He said: When I took it to exert it [to get the last of the milk], he said: "Do not do that; leave the caller of the milk."
حدثنا أسود بن عامر، حدثنا زهير، عن الأعمش، عن يعقوب بن بحير، رجل من الحي، قال: سمعت ضرار بن الأزور قال: أهدينا لرسول الله صلى الله عليه وسلم لقحة، قال: فحلبتها، قال: فلما أخذت لأجهدها قال: " لا تفعل، دع داعي اللبن "