Mishkat al-Masabih 30 Fine Qualities كتاب المناقب 187

وَعَنِ ابْنِ عَبَّاسٍ قَالَ: كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ حَامِلًا الْحَسَنَ بْنَ عليٍّ على عَاتِقه فَقَالَ رَجُلٌ: نِعْمَ الْمَرْكَبُ رَكِبْتَ يَا غُلَامُ فَقَالَ النَّبِيُّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ: «وَنِعْمَ الرَّاكِبُ هُوَ» . رَوَاهُ التِّرْمِذِيّ

Ibn `Abbas told that when God’s messenger was carrying al-Hasan b. `Ali on his shoulder a man said, “You have mounted on a fine steed, boy.” The Prophet said, “And he is a fine rider.” Tirmidhi transmitted it.