كتاب الصلاة
4
The Book of Prayers
(45)
Chapter: Moderation In Prostration; Placing The Hands On The Ground, Keeping The Elbows Up, Away From The Sides, And Lifting The Belly Up Off The Thighs When Prostrating
(45)
باب الاِعْتِدَالِ فِي السُّجُودِ وَوَضْعِ الْكَفَّيْنِ عَلَى الأَرْضِ وَرَفْعِ الْمِرْفَقَيْنِ عَنِ الْجَنْبَيْنِ وَرَفْعِ الْبَطْنِ عَنِ الْفَخِذَيْنِ فِي السُّجُودِ
Sahih Muslim 493 a

Anas reported:

The Messenger of Allah (ﷺ) said: Observe moderation in prostration, and let none of you stretch out his forearms (on the ground) like a dog.
حَدَّثَنَا أَبُو بَكْرِ بْنُ أَبِي شَيْبَةَ، حَدَّثَنَا وَكِيعٌ، عَنْ شُعْبَةَ، عَنْ قَتَادَةَ، عَنْ أَنَسٍ، قَالَ قَالَ رَسُولُ اللَّهِ صلى الله عليه وسلم ‏ "‏ اعْتَدِلُوا فِي السُّجُودِ وَلاَ يَبْسُطْ أَحَدُكُمْ ذِرَاعَيْهِ انْبِسَاطَ الْكَلْبِ ‏"‏ ‏.‏
Reference : Sahih Muslim 493 a
In-book reference : Book 4, Hadith 264
USC-MSA web (English) reference : Book 4, Hadith 997
  (deprecated numbering scheme)