Fiqh-us-Sunnah Volume 4, Funerals and Dhikr, Fiqh 4.112C.

The Prophet, peace be upon him, loved comprehensive supplications but used other supplications as well. The Qur’anic supplication, “Our Lord, give us good in this world, and give us good in the hereafter,” is just such a comprehensive supplication.

A man came to the Prophet, peace be upon him, and said, “O Messenger of Allah, which is the best supplication?” The Prophet, peace be upon him, said, “Supplicate to your Lord for forgiveness and security in this world and in the Hereafter.” He came again the next day, and then again on the following (third) day and asked him the same thing. The Prophet, peace be upon him, gave him the same answer, and then said, “If you are given forgiveness and security in this world and in the Hereafter you have attained success.” Another version says: “The Prophet, peace be upon him, said, ‘No supplication made by a person is better than asking “O Allah, I ask You for security in this world and in the Hereafter”‘.” (Ibn Majah)