Hadith: The supplication that the Prophet (may Allah's peace and blessings be upon him) recited most was: "Allāhumma rabbana ātina fi ad-dunya hasanah wa fi al-ākhirati hasanah wa qina ‘adhāb an-nār (O Allah our Lord, give us in this world that which is good and in the Hereafter that which is good and protect us from the torment of the Fire)

عَنْ أَنَسٍ رضي الله عنه قَالَ:
كَانَ أَكْثَرُ دُعَاءِ النَّبِيِّ صَلَّى اللهُ عَلَيْهِ وَسَلَّمَ: «اللَّهُمَّ رَبَّنَا آتِنَا فِي الدُّنْيَا حَسَنَةً، وَفِي الآخِرَةِ حَسَنَةً، وَقِنَا عَذَابَ النَّارِ».
[صحيح] - [متفق عليه] - [صحيح البخاري: 6389]

Anas (may Allah be pleased with him) reported
The supplication that the Prophet (may Allah's peace and blessings be upon him) recited most was: "Allāhumma rabbana ātina fi ad-dunya hasanah wa fi al-ākhirati hasanah wa qina ‘adhāb an-nār (O Allah our Lord, give us in this world that which is good and in the Hereafter that which is good and protect us from the torment of the Fire)."
[Authentic hadith] - [Narrated by Bukhari & Muslim] - [Sahih Bukhari - 6389]

Explanation

The Prophet (may Allah's peace and blessings be upon him) used to frequently recite concise supplications that were comprehensive in meaning including the following supplication: "Allāhumma rabbana ātina fi ad-dunya hasanah wa fi al-ākhirati hasanah wa qina ‘adhāb an-nār (O Allah our Lord, give us in this world that which is good and in the Hereafter that which is good and protect us from the torment of the Fire)." This supplication includes the good things in this world like a blissful, extensive, and lawful sustenance; a righteous wife; a child who is a source of joy, relief, beneficial knowledge, good deeds, and similar favorable and permissible demands. As for the good things in the Hereafter, they include safety from punishments in the grave, the standing, and the Fire, besides attaining the pleasure of Allah, winning eternal bliss, and being close to the Most Merciful Lord.