Musannaf Ibn Abi Shaybah

It is narrated from Hazrat Ibn Uyaynah. He says that I asked Hazrat Ubaidullah bin Abi Yazid: Did you attend the meals of Hazrat Ibn Abbas (may Allah be pleased with them)? He said: Yes. I asked: What did you see him do? Hazrat Ubaidullah said: I used to see him licking his three fingers.