وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ أَبِي حَازِمِ بْنِ دِينَارٍ، عَنْ سَهْلِ بْنِ سَعْدٍ، أَنَّهُ قَالَ كَانَ النَّاسُ يُؤْمَرُونَ أَنْ يَضَعَ الرَّجُلُ الْيَدَ الْيُمْنَى عَلَى ذِرَاعِهِ الْيُسْرَى فِي الصَّلاَةِ ‏.‏ قَالَ أَبُو حَازِمٍ لاَ أَعْلَمُ إِلاَّ أَنَّهُ يَنْمِي ذَلِكَ ‏.‏

Yahya related to me from Malik from Abu Hazim ibn Dinar that Sahlibn Sad said, "People used to be ordered to place their right hands ontheir left forearms in the prayer." Abu Hazim added, "I knowfor sure that Sahl traces that back to the Prophet, may Allah blesshim and grant him peace." Translation Not Available

Book Ref: Muwatta Imam Malik Book 9 Hadith 381
Web Ref:  Muwatta Imam Malik Book 9 Hadith 50

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