Abu Hurayra reported that the Prophet, may Allah bless him and grant him peace, said, “Anyone who does not show mercy to our children nor acknowledge the right of our old people is not one of us.”
حَدَّثَنَا أَحْمَدُ بْنُ عِيسَى، قَالَ‏:‏ حَدَّثَنَا عَبْدُ اللهِ بْنُ وَهْبٍ، عَنْ أَبِي صَخْرٍ، عَنِ ابْنِ قُسَيْطٍ، عَنْ أَبِي هُرَيْرَةَ، عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ‏:‏ مَنْ لَمْ يَرْحَمْ صَغِيرَنَا، وَيَعْرِفْ حَقَّ كَبِيرِنَا، فَلَيْسَ مِنَّا‏.‏
Reference : Al-Adab Al-Mufrad 353
In-book reference : Book 18, Hadith 1
English translation : Book 18, Hadith 353