Abbas bin Sahl al-Sa'idi, reporting from Abu Humayd (may Allah be pleased with him) the description of the prayer of the Messenger of Allah (peace and blessings be upon him), says: When he (peace and blessings be upon him) prostrated, he kept his legs apart and kept his belly away from his thighs.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2712