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". (JA)
English reference (JA): Book 5, Hadith 41 (JA)
Arabic reference (JA): Book 5, Hadith 42 (JA)