Why did Surat Hud turn the Messenger of Allah, may Allah bless him and grant him peace, gray?

The hadith "Hud and its sisters have made me old..." was narrated by Al-Tirmidhi and others from Ibn Abbas, and it is authentic. The reason for it is the Prophet's (peace be upon him) concern about the horrors of the Day of Resurrection and the events of past nations mentioned in the surah, which made him grow old out of fear for his Ummah.