Musnad Ahmad 947:1

'Abd al-Rahman ibn Mahdi narrated to us, Malik narrated to us, from Damrah ibn Sa'id, from 'Ubayd Allah ibn 'Abd Allah, that 'Umar ibn al-Khattab asked Abu Waqid al-Laythi: "With what did the Messenger of Allah, peace and blessings of Allah be upon him, recite during the 'Eid?" He said: "He used to recite 'Qaf' (Surah 50) and 'Iqtarabat' (Surah 54)."