Musannaf Ibn Abi Shayba 3:4804

'Abdullah ibn Idris narrated to us, from Layth ibn Sa'd, from Dinar, from Abu Hurayrah, who said: A man came and said, "Among us are those who go out (for trade) and those who strike (the earth for business), so is there any sin upon us if we sleep before the 'Isha prayer?" He said, "Yes, and a sin, and two sins, and three sins."