Abu Juhayfa R.A. says:
'The people said: "O Rasulallah, (Sallallahu alaihe wasallam)! we see the signs of old age beginning to show on you?" Rasulullah (Sallallahu alaihe wasallam) replied: "Surah Hud and similar surahs have made me old".
English reference: Book 5, Hadith 41
Arabic reference: Book 5, Hadith 42