It wasnarrated from Maimunah that when the Prophet (ﷺ) prostrated,hewould hold his forearms away from his sides, such that if a lambwanted to pass under his arms, it would be able to do so. (ID)
English reference (ID): Vol. 1, Book 5, Hadith 880 (ID)
Arabic reference (ID): Book 5, Hadith 929 (ID)