Sunan an-Nasai Book 12, Hadith 1092

أَخْبَرَنَا زِيَادُ بْنُ أَيُّوبَ، دَلُّويَهْ قَالَ حَدَّثَنَا ابْنُ عُلَيَّةَ، قَالَ حَدَّثَنَا أَيُّوبُ، عَنْ نَافِعٍ، عَنِ ابْنِ عُمَرَ، رَفَعَهُ قَالَ ‏ "‏ إِنَّ الْيَدَيْنِ تَسْجُدَانِ كَمَا يَسْجُدُ الْوَجْهُ فَإِذَا وَضَعَ أَحَدُكُمْ وَجْهَهُ فَلْيَضَعْ يَدَيْهِ وَإِذَا رَفَعَهُ فَلْيَرْفَعْهُمَا ‏"‏ ‏.‏

It was narrated from Ibn 'Umar in a Marfu' report that:The hands prostrate as the face prostrates, so when one of you puts his face down he should put his hands down, and when he raises (the face) he should raise (the hands) too