Hadith: The Messenger of Allah (may Allah's peace and blessings be upon him) used to say the following supplication: "O Allah, I seek refuge with You from the punishment of the grave, the punishment of the Fire, the trials of life and death, and the trial of the Anti-Christ."

عن أبي هُرَيْرَةَ رضي الله عنه قال: كان رسول الله صلى الله عليه وسلم يدعو: اللَّهُمَّ إني أعوذ بك من عذاب القبر، وعذاب النار، ومن فتنة الْمَحْيَا وَالْمَمَاتِ، ومن فتنة الْمَسِيحِ الدَّجَّالِ». وفي لفظ لمسلم: «إذا تَشَهَّدَ أحدكم فَلْيَسْتَعِذْ بالله من أَرْبَعٍ، يقول: اللهُمَّ إني أعوذ بك من عذاب جَهَنَّم...». ثم ذكر نحوه.
[صحيح] - [متفق عليه]

Abu Hurayrah (may Allah be pleased with him) reported: The Messenger of Allah (may Allah's peace and blessings be upon him) used to say the following supplication: "O Allah, I seek refuge with You from the punishment of the grave, the punishment of the Fire, the trials of life and death, and the trial of the Anti-Christ." The wording in Sahīh Muslim reads: "When one of you completes the Tashahhud, let him seek refuge with Allah from four things by saying: 'O Allah, I seek refuge with You from the punishment of the Hell-fire...'" mentioning words similar to those in the first Hadīth.
Sahih/Authentic. - [Al-Bukhari and Muslim]

Explanation

The Prophet (may Allah's peace and blessings be upon him) sought refuge with Allah from four things, and he commanded us to seek refuge with Allah from them after the Tashahhud. They are: the punishment of the grave, the punishment of the Fire, the desires and doubtful matters of the worldly life, and the trials of death. He sought refuge with Allah from them due to their great danger. The trials of the grave are the cause for punishment therein. The trials of life include the trials of the impostors who will appear to the people in the image of truth while they are overwhelmingly false. The one among them who will pose the most severe trial, and about whom authentic reports were transmitted, will appear in the last days. He is the Anti-Christ, and that is why the Prophet (may Allah's peace and blessings be upon him) sought refuge with Allah from him in particular.