Thabit (may Allah have mercy on him) said: Sayyiduna Anas (may Allah be pleased with him) would describe to us the prayer of the Messenger of Allah (peace and blessings be upon him): when he (peace and blessings be upon him), while praying, raised his head from bowing, he would remain standing so long that we would think that perhaps he had forgotten.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الصلاة / 2624