Rabi'a b. Ka'b said: I was with Allah's Messenger (ﷺ) one night. and I brought him water and what he required. He said to me: Ask (anything you like). I said: I ask your company in Paradise. He (the Holy Prophet) said: Or anything else besides it. I said: That is all (what I require). He said: Then help me to achieve this for you by devoting yourself often to prostration.
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا الْحَكَمُ بْنُ مُوسَى أَبُو صَالِحٍ، حَدَّثَنَا هِقْلُ بْنُ زِيَادٍ، قَالَ سَمِعْتُ الأَوْزَاعِيَّ، قَالَ حَدَّثَنِي يَحْيَى بْنُ أَبِي كَثِيرٍ، حَدَّثَنِي أَبُو سَلَمَةَ، حَدَّثَنِي رَبِيعَةُ بْنُ كَعْبٍ الأَسْلَمِيُّ، قَالَ كُنْتُ أَبِيتُ مَعَ رَسُولِ اللَّهِ صلى الله عليه وسلم فَأَتَيْتُهُ بِوَضُوئِهِ وَحَاجَتِهِ فَقَالَ لِي " سَلْ " . فَقُلْتُ أَسْأَلُكَ مُرَافَقَتَكَ فِي الْجَنَّةِ . قَالَ " أَوَغَيْرَ ذَلِكَ " . قُلْتُ هُوَ ذَاكَ . قَالَ " فَأَعِنِّي عَلَى نَفْسِكَ بِكَثْرَةِ السُّجُودِ " .
sunnah.com