Musannaf Ibn Abi Shayba 3:6343

Ishaq ibn Mansur narrated to us, he said: Muhammad ibn Muslim narrated to us, from Ibrahim ibn Maysarah, from Mujahid, who said: "If you wish to wrap your lower garment (izar) while you are wearing both a lower garment and an upper garment (rida') and you are in prayer, then let your upper garment hang loose and wrap your lower garment." I mentioned this to Tawus, and he said: "Is this better, or is that better?"