Musannaf Ibn Abi Shayba 3:93

Abu Bakr narrated to us, he said: Isma'il bin 'Ayyash narrated to us, from 'Abd Rabbih bin Zaytun, he said: I saw Umm al-Darda' raising her palms level with her shoulders when she began the prayer. And when the Imam said, "Sami' Allahu liman hamidah" (Allah hears those who praise Him), she would raise her hands and say, "Allahumma Rabbana lakal-hamd" (O Allah, our Lord, to You is the praise).