ENOfficial
'Abdullah ibn 'Amr ibn al-'As reported that it reached him 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."
Source: sunnah.com
Other translations
Arabic
حَدَّثَنَا عَلِيٌّ، قَالَ: حَدَّثَنَا سُفْيَانُ، حَدَّثَنَا ابْنُ أَبِي جُرَيْجٍ، عَنْ عُبَيْدِ اللهِ بْنِ عَامِرٍ، عَنْ عَبْدِ اللهِ بْنِ عَمْرِو بْنِ الْعَاصِ، يَبْلُغُ بِهِ النَّبِيَّ صلى الله عليه وسلم، قَالَ: مَنْ لَمْ يَرْحَمْ صَغِيرَنَا، وَيَعْرِفْ حَقَّ كَبِيرِنَا، فَلَيْسَ مِنَّا.
sunnah.com