Musnad Ahmad 847:7

'Abd al-Wahhab al-Thaqafi narrated to us, Ayyub narrated to us, from Abu Qilabah, from Qabisah, who said: The sun eclipsed, so the Messenger of Allah (peace and blessings of Allah be upon him) went out and prayed two rak'ahs, in which he prolonged the recitation. Then it cleared, and he said: "Indeed, the sun and the moon are two signs from among the signs of Allah, with which He frightens His servants. So when you see that, pray like the most recent prayer you have performed of the obligatory ones."