ENOfficial
'Amr ibn Shu'ayb reported from his grandfather that the Messenger of Allah, 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."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ عَبْدِ اللهِ، حَدَّثَنِي ابْنُ أَبِي الزِّنَادِ، عَنْ عَبْدِ الرَّحْمَنِ بْنِ الْحَارِثِ، عَنْ عَمْرِو بْنِ شُعَيْبٍ، عَنْ أَبِيهِ، عَنْ جَدِّهِ، أَنَّ رَسُولَ اللهِ صلى الله عليه وسلم قَالَ: لَيْسَ مِنَّا مَنْ لَمْ يَرْحَمْ صَغِيرَنَا، وَيَعْرِفْ حَقَّ كَبِيرِنَا.
sunnah.com