Al-Shu`bi narrates -- and also Hammad Ibn Salama from `Ammar Ibn Abi `Ammar -- that Zayd ibn Thabit intended to go on a trip, whereupon the young `Abd Allah ibn `Abbas stood humbly at his side and taking hold of the reins of his mount adopted the attitude of a humble servant in the presence of his master. Zayd said to him: "Don't, O cousin of the Prophet [sallallaahu `alaihi wa sallam]." "Thus we were commanded to treat our ulama and elders," was `Abd Allah's reply. Zayd said to him in turn: "Let me see your hand." Abdullah stretched out his hand. Zayd, taking it, kissed it and said: "Thus we were commanded to treat the members of the household of the Prophet [sallallaahu `alaihi wa sallam]." - Bayhaqi in al-Madkhal [Saheeh according to Ibn Hajar in al-Isaba (1:561 "Zayd ibn Thabit").]