Shama-il Tirmidhi Chapter 005, Hadith Number 005 (040).
Ibne Abbas R.A. reports: "Abu Bakr R.A. once said, 'O Messenger of Allah, you have become old'. (What is the reason? Due to this mild and soft temperament he ought to be young, and also according to his age he could be still called young). Rasulullah (Sallallahu alaihe wasallam) replied: "The recitation of Surahs Hud, Waaqiah, Mursalat, Amma and Kuwwirah has made me old'".
Apart form these surahs the Surahs of Al-Haaqqah, Al-Qaariah, Al- Ghaashiah etc. have also been mentioned. In short all those surahs wherein frightening matters are mentioned, e.g. Qiyaamah, (Day of judgement) Hell, the Trumpet, the punishment of evil people etc. In hadith it is stated that Rasulullah (Sallallahu alaihe wasallam) said: "If you knew what I know, you would laugh less and cry more. You would even stop going to your wives (or as he had said)". It is written in the Sharhus Sunnah that a person saw Rasulullah (Sallallahu alaihe wasallam) in his dream. He asked: "O Rasulallah, (Sallallahu alaihe wasallam)! This hadith has reached me, that you said: 'Surah Hud has made me old'". Rasulullah (Sallallahu alaihe wasallam) replied: "There is one verse in it 'Wastaqim kama umirta' (Stay steadfast on the religion as I have commanded you). And it is well-known that to stay steadfast on the commandments of Allah is very difficult". That is why the Sufiya have written that to remain steadfast is better than a thousand miracles.