"Anas bin Malik was asked about the takbir in the prayer. He said: "The takbir should be said when bowing, when prostrating, when raising one's head from prostration and when standing up following the first two rak'ahs.' Hutaim said: 'From whom did you learn this?' He said: 'From the Prophet ﷺ, Abu Bakr and 'Umar, may Allah (SWT) be pleased with them.' Then he fell silent and Hutaim said to him: 'And 'Uthman?' He said: 'And 'Uthman.'" (Using translation from Nasāʾī 1179)
إِذَا رَكَعَ وَإِذَا سَجَدَ وَإِذَا رَفَعَ رَأْسَهُ مِنَ السُّجُودِ وَإِذَا سَجَدَ وَإِذَا قَامَ فِي الرَّكْعَتَيْنِ فَقَالَ لَهُ خَطِيمٌ عَمَّنْ تَحْفَظُ هَذَا؟ فَقَالَ عَنِ النَّبِيِّ ﷺ وَأَبِي بَكْرٍ وَعُمَرَ ؓ فَقَالَ لَهُ خَطِيمٌ وَعُثْمَانَ؟ قَالَ وَعُثْمَانَ هَذَا هُوَ الصَّوَابُ بِالْخَاءِ الْمُعْجَمَةِ وَقِيلَ حَطِيمٌ بِالْحَاءِ