Musannaf Ibn Abi Shayba 18:991

Abu Bakr narrated to us, he said: Muhammad ibn Fudayl narrated to us, from Abu Husayn, from al-Sha’bi, who said: If there is a dog in the house, and the people of the house give permission to a man, and he enters, and it bites him, they are liable. But if he enters without permission, and it bites him, they are not liable.