Usamah ibn Zayd reported: The Messenger of Allah, peace and blessings be upon him, would put me on one of his thighs and he would put Hasan ibn Ali on his other thigh. Then, the Prophet would hug us and he would say, “O Allah, be merciful to them as I am merciful to them.”
Source: Ṣaḥīḥ al-Bukhārī 5657
Grade: Sahih (authentic) according to Al-Bukhari
عَنْ أُسَامَةَ بْنِ زَيْدٍ رَضِيَ اللَّهُ عَنْهُمَا كَانَ رَسُولُ اللَّهِ صَلَّى اللَّهُ عَلَيْهِ وَسَلَّمَ يَأْخُذُنِي فَيُقْعِدُنِي عَلَى فَخِذِهِ وَيُقْعِدُ الْحَسَنَ عَلَى فَخِذِهِ الْأُخْرَى ثُمَّ يَضُمُّهُمَا ثُمَّ يَقُولُ اللَّهُمَّ ارْحَمْهُمَا فَإِنِّي أَرْحَمُهُمَا
5657 صحيح البخاري كتاب الأدب باب وضع الصبي على الفخذ