It is narrated from Hazrat Abu Saeed (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: When any one of you enters a garden and wants to eat, he should call the owner of the garden three times. If he comes, very good; otherwise, he may eat alone. Similarly, when any one of you passes by a camel and wants to drink its milk, he should call the owner of the camel. If he comes, very good; otherwise, he may drink its milk. And hospitality is for three days; whatever is beyond that is charity.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 11045
Hadith Gradingحکم دارالسلام:حديث حسن، مؤمل بن إسماعيل -وإن كان سيئ الحفظ - متابع، وله شواهد تقويه .