What did the Prophet Muhammad (saw) not disapprove of, when `Umar swore by Allah in his presence?
 Narrated Muhammad bin Al-Munkadir:                     I saw Jabir bin `Abdullah swearing by Allah that Ibn Sayyad was the Dajjal. I said to Jabir, "How can you swear by Allah?" Jabir said, "I have heard `Umar swearing by Allah regarding this matter in the presence of the Prophet and the Prophet did not disapprove of it."