Musannaf Ibn Abi Shayba 3:4685

Waki’ narrated to us, from Sufyan, from Maysarah al-Hudhali (al-Nahdi), from al-Minhal, from Abu Ubaydah, who said: Abdullah went out from his house to the mosque, and there was a man praying, having placed his feet together. Abdullah said: "As for this one, he has missed the Sunnah. If he had alternated between his feet, it would have been more beloved to me."