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Qurʾān Bukhārī Muslim Nasāʾī Abū Dāwūd Tirmidhī Ibn Mājah Mālik Aḥmad Dārimī Ḥākim Ibn Ḥibbān Ṭabarānī Nasāʾī's Kubrá Bayhaqī al-Luʾluʾ wa-al-Marjān Ibn Rajab's Fifty Riyāḍ al-Ṣāliḥīn Aḥmad's Zuhd Suyūṭī
nasai-kubra:748 – al-Rabīʿ b. Sulaymān b. Dāwud > Isḥāq b. Bakr from my father > ʿAmr b. al-Ḥārith > Yaḥyá > al-Qāsim > ʿAbdullāh / Ibn ʿAbdullāh b. ʿUmar from his father > from Sunnah al-Ṣalāh

His father (Ibn 'Umar) said: "One of the sunnahs of the prayer is to hold the right foot upright and point its toes toward the Qiblah, and to sit on the left foot." (Using translation from Nasāʾī 1158)  

الكبرى للنسائي:٧٤٨ – أَخْبَرَنِي الرَّبِيعُ بْنُ سُلَيْمَانَ بْنِ دَاوُدَ قَالَ حَدَّثَنَا إِسْحَاقُ بْنُ بَكْرٍ قَالَ حَدَّثَنَا أَبِي عَنْ عَمْرِو بْنِ الْحَارِثِ عَنْ يَحْيَى أَنَّ الْقَاسِمَ حَدَّثَهُ عَنْ عَبْدِ اللهِ وَهُوَ ابْنُ عَبْدِ اللهِ بْنِ عُمَرَ عَنْ أَبِيهِ قَالَ «§مِنْ سُنَّةِ الصَّلَاةِ

أَنْ يَنْصِبَ الْقَدَمَ الْيُمْنَى وَاسْتِقْبَالُهُ بِأَصَابِعِهَا الْقِبْلَةَ وَالْجُلُوسُ عَلَى الْيُسْرَى»  

See similar narrations below:

Collected by Nasāʾī
nasai:1158 – al-Rabīʿ b. Sulaymān b. Dāwud > Isḥāq b. Bakr b. Muḍar from my father > ʿAmr b. al-Ḥārith > Yaḥyá > al-Qāsim > ʿAbdullāh / Ibn ʿAbdullāh b. ʿUmar from his father > from Sunnah al-Ṣalāh

His father (Ibn 'Umar) said: "One of the sunnahs of the prayer is to hold the right foot upright and point its toes toward the Qiblah, and to sit on the left foot."  

النسائي:١١٥٨ – أَخْبَرَنَا الرَّبِيعُ بْنُ سُلَيْمَانَ بْنِ دَاوُدَ قَالَ حَدَّثَنَا إِسْحَاقُ بْنُ بَكْرِ بْنِ مُضَرَ قَالَ حَدَّثَنِي أَبِي عَنْ عَمْرِو بْنِ الْحَارِثِ عَنْ يَحْيَى أَنَّ الْقَاسِمَ حَدَّثَهُ عَنْ عَبْدِ اللَّهِ وَهُوَ ابْنُ عَبْدِ اللَّهِ بْنِ عُمَرَ عَنْ أَبِيهِ قَالَ مِنْ سُنَّةِ الصَّلاَةِ

أَنْ تَنْصِبَ الْقَدَمَ الْيُمْنَى وَاسْتِقْبَالُهُ بِأَصَابِعِهَا الْقِبْلَةَ وَالْجُلُوسُ عَلَى الْيُسْرَى