Sunan an-Nasa'i, hadith 892

أَخْبَرَنَا عَمْرُو بْنُ عَلِيٍّ، قَالَ حَدَّثَنَا يَحْيَى، عَنْ سُفْيَانَ بْنِ سَعِيدٍ الثَّوْرِيِّ، عَنْ مَيْسَرَةَ، عَنِ الْمِنْهَالِ بْنِ عَمْرٍو، عَنْ أَبِي عُبَيْدَةَ، أَنَّ عَبْدَ اللَّهِ، رَأَى رَجُلاً يُصَلِّي قَدْ صَفَّ بَيْنَ قَدَمَيْهِ فَقَالَ خَالَفَ السُّنَّةَ وَلَوْ رَاوَحَ بَيْنَهُمَا كَانَ أَفْضَلَ ‏.‏

It was narrated from Abu Ubaidah that:Abdullah saw a man who was praying with his feet together. He said: "He is going against the Sunnah; if he shifted his weight from one to the other that would be better