Al-Bara’ b. ‘Azib reported God's Messenger as saying, “When you prostrate yourself, place the palms of your hands on the ground and raise your elbows.”
Anas reported God’s Messenger as saying, “Adopt a moderate position when prostrating yourselves, and see that none of you stretches out his forearms like a dog.”
Narrated Maimuna said that when the Prophet prostrated himself he kept his arms so far away from his sides that if a lamb had wanted to pass under his arms it could have done so.
This is Abu Dawud’s wording, as explained in Sharh as-sunna with his isnad. Muslim has something to the same effect:
She said that when the Prophet prostrated himself, if a lamb had wanted to pass between his arms it could have done so.
