Hadith 319
Sayyiduna Anas (may Allah be pleased with him) narrates: (On one occasion) the Prophet Muhammad (peace and blessings be upon him) faced some discomfort. The next morning, it was said to him: O Messenger of Allah! The signs of discomfort are evident upon you. The Prophet Muhammad (peace and blessings be upon him) said: My condition is as you see, (in this state) I recited seven long surahs (in voluntary prayers) last night.