The Gemara read , "And they said to him, 'Where is Sarah your wife?' And he said, 'Behold, she is in the tent,'" to teach us that Sarah was modest (and therefore kept secluded). Rav Judah said in Rav's name that the ministering angels knew that Sarah was in the tent, but they brought out the fact that she was in the tent to make her more beloved to Abraham (by impressing him with her modesty). Rabbi Jose son of Rabbi Hanina said that they brought out the fact that she was in the tent to send her the wine-cup of benediction. (The wine-cup over which the Grace after Meals is recited and which is partaken by all the guests.)