He saw the Prophet ﷺ, when he started to pray, raise his hands until his thumbs were almost level with his earlobes.  

أَنَّهُ رَأَى النَّبِيَّ ﷺ إِذَا افْتَتَحَ الصَّلاَةَ رَفَعَ يَدَيْهِ حَتَّى تَكَادَ إِبْهَامَاهُ تُحَاذِي شَحْمَةَ أُذُنَيْهِ