It is narrated from Sayyiduna Dhirar bin Azwar (may Allah be pleased with him) that once the Prophet (peace and blessings of Allah be upon him) passed by him while he was milking (an animal). The Prophet (peace and blessings of Allah be upon him) said: Leave enough milk in its udders so that it can be obtained again.
Hadith Referenceمسند احمد / مسند المدنيين رضي الله عنهم اجمعين / 16702
Hadith Gradingحکم دارالسلام:إسناده ضعيف لجهالة حال يعقوب بن بحير، والأعمش مدلس وما ذكر سماعا، ويعقوب لم يذكر سماعه من ضرار