Musannaf Ibn Abi Shaybah 5077 — People who are naked when the prayer

It is narrated from Mujahid that Umar bin Abd al-Aziz asked him about people whose boat breaks apart and they come out, and then the time of prayer comes (and they have no clothes on their bodies): what should they do? Mujahid said: Their imam will be on their left side. They will all form a single row, and each man will cover his private parts with his left hand, but without touching them.