Sahih Ibn Khuzaymah

It is narrated from Sayyiduna Ali (may Allah be pleased with him) that when a solar eclipse occurred, Sayyiduna Ali (may Allah be pleased with him) led the people in the eclipse prayer. He began the prayer and recited Surah « يٰس » or a similar surah, then he performed a bowing (ruku) as long as the length of the surah, then when he raised his head from ruku, he said « سَمِعَ اللهُ لِمَنْ حَمِدَهُ », then he stood for a duration equal to the recitation of the surah, supplicating and saying takbeer. Then he performed another long ruku equal to his recitation. Then the rest of the hadith is mentioned, and he said: Then when he stood for the second rak’ah, he did all the actions as in the first rak’ah. Then he informed those present that the Messenger of Allah (peace and blessings be upon him) used to do likewise. Imam Abu Bakr (may Allah have mercy on him) says that it is mentioned in this narration that Sayyiduna Ali (may Allah be pleased with him) performed four rukus in each rak’ah, as is mentioned in the narration of Tawus from Sayyiduna Ibn Abbas (may Allah be pleased with them both).