Mishkat al-Masabih
Book 30, Hadith 157
Arabic hadith text
وَعَنِ الْبَرَاءِ قَالَ: رَأَيْتُ النَّبِيَّ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ وَالْحَسَنُ بْنُ عَلِيٍّ عَلَى عَاتِقِهِ يَقُولُ: «اللَّهُمَّ إِنِّي أُحِبُّهُ فَأَحِبَّهُ» مُتَّفق عَلَيْهِ
Translation
Al-Bara' told that he saw the Prophet with al-Hasan b. `Ali on his shoulder saying, "O God, I love him, so I beseech Thee to love him." Bukhari and Muslim.