What is the Du`a' Ma'thur (supplication based on transmitted reports) that we should recite
before and after Taslim (salutation of peace ending the Prayer)?
Abu Hurayrah (may Allah be pleased with him) narrated that the Messenger of Allah (peace be upon him) said:
When anyone of you utters the (last) Tashahhud (testification recited in the sitting position in the last unit of Prayer), they must seek refuge with Allah from four (trials), saying, 'O Allah, I seek refuge with You from the torment of Hell, from the torment of the grave, from the trial of life and death and from the evil of the trial of Al-Masih-ul-Dajjal.'
This is the wording of
Muslim; Book on Al-Masajid (Mosques), chapter on "Things a Worshiper Seeks Refuge from during Salah."
Al-Bukhari related the same Hadith in the Book on Al-Jana'iz (Funerals), chapter on "Seeking Refuge with Allah from the Torment of the Grave"; his version mentions seeking refuge with Allah from trials, but does not include the Tashahhud part.
Abu Dawud related it in the Book on Salah, chapter on "What is to be said after Tashahhud"; according to his narration, the Prophet (peace be upon him) said:
When anyone of you completes the (last) Tashahhud, they should seek refuge with Allah from four (trials)...
Al-Nasa'y related it in the Book on Al-Sahw (Forgetfulness), chapter on "Another way of seeking refuge with Allah from trials during Salah" with the addition
Then they may supplicate for whatever they wish for themselves.
Further on this subject,
in the Book on Salah, chapter on "Al-Tashahhud",
Abu Dawud reported `Abdullah ibn Mas`ud (may Allah be pleased with him) to have said that the Messenger of Allah (peace be upon him) used to teach them to say the following Du`a' after Tashahhud:
O Allah, join our hearts, mend our relationships, guide us to the path of peace, bring us out of darkness into light, save us from sins, outward or inward, and bless our ears, eyes, hearts, spouses and children. Accept our repentance; it is You Who accepts repentance, the Most Merciful. And make us grateful for Your Blessing; make us praise it while accepting it and complete Your Favor upon us.
(Part No. 7; Page No. 63)
Al-Hakim related the same Hadith in Al-Mustadrak through two different Sanads (chains of narrators), and ranked it as Sahih;
Al-Dhahaby concurred with that.
May Allah grant us success. May peace and blessings be upon our Prophet Muhammad, his family and Companions.