Muwatta Malik · Hadith 393
وَحَدَّثَنِي عَنْ مَالِكٍ، عَنْ نَافِعٍ، أَنَّ ابْنَ عُمَرَ، لَمْ يَكُنْ يَلْتَفِتُ فِي صَلاَتِهِ .
Yahya related to me from Malik from Nafi that Ibn Umar would never turn around when praying
Mauquf Sahih · Salim al-Hilali