Musnad Ahmad 5:649

Yahya ibn Adam narrated to us, Zuhayr narrated to us, al-Hasan ibn al-Hurr narrated to us, al-Hakam ibn Utaybah narrated to us, from a man called Hanash, from Ali, who said: "The sun eclipsed, so Ali prayed with the people. He recited [Surah] Yasin or something similar to it. Then he bowed for an amount equal to the length of a surah. Then he raised his head and said, 'Allah hears those who praise Him.' Then he stood for the length of the surah, supplicating and saying 'Allahu Akbar.' Then he bowed for the length of his recitation as well. Then he said, 'Allah hears those who praise Him.' Then he stood again for the length of the surah, then he bowed for the length of that as well, until he had prayed four bowings [in one rak'ah]. Then he said, 'Allah hears those who praise Him,' and then he prostrated. Then he stood for the second rak'ah and did as he had done in the first rak'ah. Then he sat supplicating and beseeching until the sun cleared." Then he told them that the Messenger of Allah (peace and blessings of Allah be upon him) did likewise.