Narrated Abu Huraira: I heard Allah's Messenger (ﷺ) saying, Allah divided Mercy into one hundred parts. He kept ninety nine parts with Him and sent down one part to the earth, and because of that, its one single part, His Creations are merciful to each other, so that even the mare lifts up its hoofs away from its baby animal, lest it should trample on it."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا الْحَكَمُ بْنُ نَافِعٍ، أَخْبَرَنَا شُعَيْبٌ، عَنِ الزُّهْرِيِّ، أَخْبَرَنَا سَعِيدُ بْنُ الْمُسَيَّبِ، أَنَّ أَبَا هُرَيْرَةَ، قَالَ سَمِعْتُ رَسُولَ اللَّهِ صلى الله عليه وسلم يَقُولُ " جَعَلَ اللَّهُ الرَّحْمَةَ مِائَةَ جُزْءٍ، فَأَمْسَكَ عِنْدَهُ تِسْعَةً وَتِسْعِينَ جُزْءًا، وَأَنْزَلَ فِي الأَرْضِ جُزْءًا وَاحِدًا، فَمِنْ ذَلِكَ الْجُزْءِ يَتَرَاحَمُ الْخَلْقُ، حَتَّى تَرْفَعَ الْفَرَسُ حَافِرَهَا عَنْ وَلَدِهَا خَشْيَةَ أَنْ تُصِيبَهُ ".
sunnah.com