What is the recommended manner of prostration regarding the arms and body posture?
Chapter on the Description of Prayer
Al-Mughni
Book of Prayer
Primary text
It is sunnah for the worshipper to separate his upper arms from his sides and his abdomen from his thighs when prostrating, as the Prophet, peace be upon him, used to do so. The standard reported is that he would separate his upper arms from his sides. Abu Ishaq Al-Sha'bi described the prostration as placing the hands on the ground, raising the buttocks, and the Prophet used to be 'jakh' (hollow/uplifted) in prostration. Abu Abdillah (Ahmad) mentioned that it is reported about the Prophet, peace be upon him, that if a quadruped animal passed underneath him while prostrating, it could pass through, due to the intensity of raising his elbows and upper arms. This lifting of the arms is opposed to the spreading of the forearms like a dog, which is forbidden.
Supporting text
It is prohibited to spread the forearms on the ground like a dog's sprawling, as established by the Hadith stating, "When one of you prostrates, let him be upright, and not spread his forearms like a dog's spreading," which is deemed Hasan Sahih. Another narration states that one should prostrate without spreading or clenching them, and to raise the elbows.