Bava Batra, Chapter Five, Mishnah Nine
Mishnah nine deals with a father who sends his small child to buy oil from a shopkeeper and on the way home the son drops the flask of oil.
1) If a man sent his child to a shopkeeper with a pondion (a coin) in his hand and he measured him out an issars (a coin worth half a pondion) worth of oil and gave him an issar in change and the child broke the flask and lost the issar, the shopkeeper is liable.
a) Rabbi Judah declares him exempt, since the father sent the child for this purpose.
b) And the Sages agree with Rabbi Judah that if the flask was in the childs hand, and the shopkeeper measured the oil into it, the shopkeeper is exempt.
In the scenario in our mishnah a father sends his child to a store to buy him some oil. The shopkeeper hands him a flask containing the requested oil and the change from the sale. According to the Sages, if the child should lose the oil or the coin on his return home, the shopkeeper is liable to pay back the father. Since a child is not responsible for his actions, the shopkeeper should have found a safer way of returning the oil and coin to the father. Rabbi Judah disagrees. According to him, since the father sent the child on such a mission, the father agreed to allow his child to deliver the oil and the change. The Sages agree with Rabbi Judah that the shopkeeper is not liable only in the case where the child came to the store with a flask in his hand. In such a case it is clear that the father intended that the child should deliver the oil, and therefore the shopkeeper will be exempt.