Musnad Ahmad 26:836

Ya'qub narrated to us, my father narrated to us, from Ibn Ishaq, Al-Harith ibn Fudayl al-Ansari, then al-Khatmi, narrated to us, from Sufyan ibn Abi al-Awja' al-Sulami, from Abu Shurayh al-Khuza'i, who said: The sun eclipsed during the time of Uthman ibn Affan, and Abdullah ibn Mas'ud was in Medina. He said: So Uthman went out and led the people in that prayer, two rak'ahs, with two prostrations in every rak'ah. He said: Then Uthman departed and entered his house, and Abdullah ibn Mas'ud sat by the chamber of Aisha, and we sat with him. He said: "Indeed, the Messenger of Allah, peace and blessings of Allah be upon him, used to command us to pray at the eclipse of the sun and the moon. So when you see that something has afflicted them, hasten to prayer. For if it is that which you fear, it will be while you are not in a state of heedlessness; and if it is not, you will have attained good and earned it."