Sunan of Abu Dawood Book 2, Hadith 867

حَدَّثَنَا حَفْصُ بْنُ عُمَرَ، حَدَّثَنَا شُعْبَةُ، عَنْ أَبِي يَعْفُورٍ، - قَالَ أَبُو دَاوُدَ وَاسْمُهُ وَقْدَانُ - عَنْ مُصْعَبِ بْنِ سَعْدٍ، قَالَ صَلَّيْتُ إِلَى جَنْبِ أَبِي فَجَعَلْتُ يَدَىَّ بَيْنَ رُكْبَتَىَّ فَنَهَانِي عَنْ ذَلِكَ، فَعُدْتُ فَقَالَ لاَ تَصْنَعْ هَذَا فَإِنَّا كُنَّا نَفْعَلُهُ فَنُهِينَا عَنْ ذَلِكَ وَأُمِرْنَا أَنْ نَضَعَ أَيْدِيَنَا عَلَى الرُّكَبِ ‏.‏

Mus'ab b sa'd said:I prayed by the side of my father. I put both of my hands between my knees(in bowing condition). He prohibited me from it. I then repeated; so he said: Do not do so, because we used to do so. But we were prohibited to do that, and commanded to put our hands on the knees