Babylonian Talmud, Tractate Brachot 37b

Rabbi Joseph said: If in a soup there are pieces of bread as big as an olive, the blessing said before it is ‘Who brings forth bread from the earth,’ and the blessing said afterwards is the full Birkat Hamazon (which includes three blessings). If there are no pieces as big as an olive in it, the blessing said before it is ‘Who creates various kinds of foods’, and after it is Al Hamechiya (a shorter grace after meals which summarizes three blessings). Said Rabbi Joseph: Whence do I derive this? Because it has been taught: If one is in the act of making a meal-offering in Jerusalem, he says, ‘Blessed is the one who has kept us alive and preserved us and brought us to this season’. When he takes them up in order to eat them, he says the blessing, ‘Who brings forth bread from the earth’. And it was taught in connection with this [story], that the offering was broken into fragments of the size of an olive. [translation by Hazon]