Musannaf Ibn Abi Shayba 3:2140

Yahya ibn Sa'id narrated to us, from Ibn 'Ajlan, from Makhul, that Abu al-Darda' led them in prayer in a *saqifah* (covered structure) in the Levant while they were traveling. He said: Then it rained upon them, reaching them. When he prayed and gave the salutation, he said: "Was there not a jurist among the people who would say, 'O man, shorten [the prayer], for we have been rained upon'?"