The Messenger of Allah ﷺ said, "No one should milk another person's livestock without his permission. Would any of you like for someone to come to his storeroom, break open his cupboard, and carry off his food? The udders of their livestock store their food for them, so no one should milk another person's livestock except with his permission."
أن رسول الله ﷺ قال: لا يحتلبن أحد ماشية أحد بغير إذنه، أيحب أحدكم أن تؤتى مشربته فتكسر خزانته، فينتقل طعامه، وإنما تخزن لهم ضروع مواشيهم أطعمتهم، فلا يحتلبن أحد ماشية أحد إلا بإذنه.
Malik narrated it in al-Istidhan (17) from Nafi, from Abdullah bin Umar, who said what has been mentioned. Bukhari narrated it in al-Luqata (2435), and Muslim in al-Luqata (1726), both from the hadith of Malik with the same chain.