Al-Kāfi - Volume 3 > Preferences for Relatives and Those of Them to Whom Zakat Cannot Be Paid
Hadith #6

6ـ أَحْمَدُ بْنُ إِدْرِيسَ وَغَيْرُهُ عَنْ مُحَمَّدِ بْنِ أَحْمَدَ عَنْ مُحَمَّدِ بْنِ عَبْدِ الْحَمِيدِ عَنْ أَبِي جَمِيلَةَ عَنْ زَيْدٍ الشَّحَّامِ عَنْ أَبِي عَبْدِ الله (عَلَيْهِ الْسَّلام) قَالَ فِي الزَّكَاةِ يُعْطَى مِنْهَا الأخُ وَالأخْتُ وَالْعَمُّ وَالْعَمَّةُ وَالْخَالُ وَالْخَالَةُ وَلاَ يُعْطَى الْجَدُّ وَلاَ الْجَدَّةُ.

6. Ahmad ibn Idris and others have narrated from Ahmad ibn Muhammad ibn Ahmad from Muhammad ibn ‘Abd al-Hamid from abu Jamilah from Zayd al-Shahham who has said the following: “Abu ‘Abd Allah, ‘Alayhi al-Salam, has said, ‘Zakat can be given to one’s brother, sister, uncle, aunt (paternal and maternal); but it cannot be given to grandfather and grandmother.’”