Sunan Ibn Majah Book 5, Hadith 89
The Messenger of Allah (ﷺ) said:
“When
anyone of you prostrates let him be balanced in prostration, and
not
spread his arms as a dog does.”
“The Messenger of Allah (ﷺ) said: ‘When anyone of you bows, let him say in his bowing: “Subhana Rabbiyal-‘Azim (Glory is to my Lord, the Most Great)” three times; if he does that his bowing will be complete. And when anyone of you prostrates, let him say in his prostration, ‘Subhana Rabbiyal-A’la (Glory if to my Lord, the Most High)” three times; if he does that, his prostration will be complete, and that is the minimum.’”
“Be balanced in prostration; none of you should prostrate with his arms spread out like a dog.”