Al-Kāfi
Hadith 1191عَنْهُ عَنْ أَحْمَدَ بْنِ مُحَمَّدِ بْنِ أَبِي نَصْرٍ عَنْ حَمَّادِ بْنِ عُثْمَانَ وَ مُحَمَّدِ بْنِ سُوقَةَ عَنْ أَبِي عَبْدِ اللَّهِ ( عليه السلام ) قَالَ السَّوِيقُ يَهْضِمُ الرُّءُوسَ .
10. It is narrated from the narrator of the previous Hadith from Ahmad ibn Muhammad from ibn abu Nasr from Hammad ibn ‘Uthaman and Muhammad ibn Sawqah who has said the following: “Abu ‘Abd Allah (a.s.), has said, sawiq digests heads (hard to digest food).”’ (See also Hadith 1 above).