He saw a man fidgeting during his prayer, so Ibn Umar said, "Do not fidget in your prayer. Do as the Messenger of Allah ﷺ used to do."Muhammad said that Ibn Umar then placed his right thigh over his left, his left hand on his left knee, and his right hand on his right knee, and pointed with his finger.
حدثنا محمد بن جعفر وحجاج المعنى قالا حدثنا شعبة حدثنا مسلم بن أبي مريم قال حجاج من بني أمية قال سمعت عبد الرحمن بن علي قال حجاج الأموي قال سمعت
ورأى رجلا يعبث في صلاته فقال ابن عمر لا تعبث في صلاتك واصنع كما كان رسول الله ﷺ يصنع قال محمد فوضع ابن عمر فخذه اليمنى على اليسرى ويده اليسرى على ركبته اليسرى ووضع يده اليمنى على اليمنى وقال بإصبعه
Its isnad is sahih. Muslim bin Abu Maryam has already had his reliability established at 1166. In Tahdhib it says he was a client of the Ansar, though another account gives a different affiliation for him. In Kabir by Bukhari, 1/273/4, it says he was a client of Banu Salim, from Madinah. Perhaps what is stated here, that he was from Banu Umaya, represents the other view regarding his affiliation.Bukhari also said, "This Muslim has scarce reports, he has no substantial body of hadith." What he means by "scarce reports" is that his hadith are few, as Ibn Saad phrased it, "He was trustworthy, with few hadith."As for Abdul-Rahman bin Ali Al-Umawi, he is Ali bin Abdul-Rahman Al-Muawi, with a damma on the meem and a light ain, in reference to Muawiya. His reliability was already established at 4575. However, Shuba made an error in his name and reversed it, as Abu Awana stated explicitly in his Sahih, the work extracted from Sahih Muslim, which is Musnad Abu Awana, 2:224. He narrated it through Abu Attab and Wahb bin Jareer, both from Shuba, from Muslim bin Abu Maryam, and said, "The two of them said, on the authority of Shuba, Abdul-Rahman bin Ali, and this is a mistake," as stated by Abu Awana.This hadith has already appeared in abbreviated form at 4570, from Sufyan, from Ibn Abu Maryam, with the correct name, and it will come again in full, also with the correct name, through Malik, from Ibn Abu Maryam, at 5331.