Imam Al-Hakim (may Allah have mercy on him) narrates: Our teacher Abu Al-Walid (may Allah have mercy on him) showed us his ring, on which was engraved: "Allah is the reliance of Hassan bin Muhammad."

Abu Al-Walid says: Our teacher Abdul Malik bin Muhammad bin Adi (may Allah have mercy on him) showed us his ring, on which was engraved: "Allah is the reliance of Abdul Malik bin Muhammad."

Abdul Malik says: Our teacher Rabi bin Sulaiman (may Allah have mercy on him) showed us his ring, on which was engraved: "Allah is the reliance of Al-Rabi bin Sulaiman."

Rabi says: Our teacher Al-Shafi'i (may Allah have mercy on him) showed us his ring, on which was engraved: "Allah is the reliance of Muhammad bin Idris."

(Tabaqat 'Ulama al-Hadith by Ibn Abd al-Hadi: 3/90)