Allaahumma inniii as’aluka iimaanan laa yartaddu wa na’iiman la yanfadu wa muraafaqata nabiyyinaa Muhammadin sallAllaahu ‘alayhi wa sallama fii a’laa darajatil-Jannati Jannatil-khuld. (‘Abdullah ibn Mas’ud. Kanz al-‘Ummal #5088; Ibid. Mustadrak Hakim #128/1928)
O Allah, I beg You for the faith that will not be shaken, the blessings that will not end, and the company of our Prophet Muhammad (sallallahu alayhi wa sallem) in the highest section of the eternal Paradise.
This du’aa has a very moving background. One night the Prophet (sallallahu alayhi wa sallem) was walking with his Companions when they passed by ‘Abdullah ibn Mas’ud (ra) who was reciting the Qur’an in his nafl salaat. As they stopped to listen, the Prophet (sallallahu alayhi wa sallem) commented that ‘Abdullah recited the Qur’an so tenderly as it was revealed. As ‘Abdullah finished his salaat and was making supplications, the Prophet (sallallahu alayhi wa sallem) exclaimed twice: “Ask and you will be given!” Sayyidnaa ‘Abdullah ibn Mas’ud (ra) was later asked what du’aa he was making at that time. He replied with this one.
(Source: Khalid Baig’s commentary to du’aa #69 in the Accepted Whispers: Munajat-e-Maqbul)