Abu Hurayra said, "A man came to the Prophet, may Allah bless him and grant him peace, with a child which he began to embrace. The Prophet, may Allah bless him and grant him peace, said. 'Do you show mercy towards me?' 'Yes,' the man replied. He said, 'Allah is more merciful towards you than you are towards this child. He is the Most Merciful of the merciful.;:
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا عَبْدُ اللهِ بْنُ مُحَمَّدٍ، قَالَ: حَدَّثَنَا مَرْوَانُ، قَالَ: حَدَّثَنَا يَزِيدُ بْنُ كَيْسَانَ، عَنْ أَبِي حَازِمٍ، عَنْ أَبِي هُرَيْرَةَ قَالَ: أَتَى النَّبِيَّ صلى الله عليه وسلم رَجُلٌ وَمَعَهُ صَبِيٌّ، فَجَعَلَ يَضُمُّهُ إِلَيْهِ، فَقَالَ النَّبِيُّ صلى الله عليه وسلم: أَتَرْحَمُهُ؟ قَالَ: نَعَمْ، قَالَ: فَاللَّهُ أَرْحَمُ بِكَ مِنْكَ بِهِ، وَهُوَ أَرْحَمُ الرَّاحِمِينَ.
sunnah.com