Narrated Jarir: Allah's Messenger (ﷺ) did not screen himself from me since my embracing Islam, and whenever he saw me he would receive me with a smile. Once I told him that I could not sit firm on horses. He stroke me on the chest with his hand and said, "O Allah! Make him firm and make him a guiding and a rightly guided man."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنِي مُحَمَّدُ بْنُ عَبْدِ اللَّهِ بْنِ نُمَيْرٍ، حَدَّثَنَا ابْنُ إِدْرِيسَ، عَنْ إِسْمَاعِيلَ، عَنْ قَيْسٍ، عَنْ جَرِيرٍ ـ رضى الله عنه ـ قَالَ مَا حَجَبَنِي النَّبِيُّ صلى الله عليه وسلم مُنْذُ أَسْلَمْتُ، وَلاَ رَآنِي إِلاَّ تَبَسَّمَ فِي وَجْهِي. وَلَقَدْ شَكَوْتُ إِلَيْهِ إِنِّي لاَ أَثْبُتُ عَلَى الْخَيْلِ. فَضَرَبَ بِيَدِهِ فِي صَدْرِي وَقَالَ " اللَّهُمَّ ثَبِّتْهُ وَاجْعَلْهُ هَادِيًا مَهْدِيًّا ".
sunnah.com