There is a tradition that when Amir al-Mu'mineen Ali sojourned in the country of Yaman, preached, and taught the ordinances of Islam, and Ka'bul-akhbar had been informed of his eloquence, he donned a robe, mounted a camel, and proceeded in company of one of the Ulama of the Jews, who was his co-religionist, to the assembly of the Amir, who at the time they entered, happened to be preaching and uttering the words, 'There are men who can see in the night, but not in the day,' and Ka'bul-akbar said: 'He speaks the truth.' Afterwards the illustrious Commander said: 'Whoever gives with a short hand will be requited with a long hand.' Ka'b again manifested his approbation, but his Jewish companion asked him how he could approve of sentiments the meaning whereof is ambiguous? Ka'b, however, replied: 'The man who sees in the night, but not in the day, is he who believes in the first book [i.e., the Pentateuch] but not in the last [i.e., the Holy Qur'an]. He who sees neither in the night nor in the day is a man who believes in neither; and the other assertion is [likewise] plain, because with Allah the Most High and Glorious alms are acceptable, and He returns them abundantly.' Meanwhile a mendicant begged something from Ka'b, who immediately divested himself of his cloak and surrendered it to him. The Jewish priest was so displeased with this act that he immediately left Ka'b, and returned to his home.
After his departure a woman approached Ka'b, and said: 'Who will give me his camel, and will take mine instead?' Ka'b replied: If thou wilt give thy cloak in addition to it, I shall agree to the exchange.' The woman having assented Ka'b donned her cloak, mounted the camel, went after the priest, and when she had reached him, said: 'Who gives with a short hand is requited with a long hand.' Then Ka'b again returned, waited on the Amir, and inquired about his Holy and Prophet Lordship (Nabi Muhammad, s.a.s.). 'Ali (r.a.a.) complied with his request, beginning to enumerate the qualities of his lordship, but Ka'b smiled, and when Ali the Commander of the Faithful asked him for the reason, he replied: 'I smile because in ancient books we find the qualities of Muhammad (s.a.s.) to agree with those thou art describing.' Then Ka'bul-akhbar made his profession of the Faith, and learnt the ordinances of Islam through 'Ali the Commander of the Faithful according to the best of his ability, remained in Yaman, made it his business to propogate the doctrines and tenets of the noble religion, but came to Madinah during the Khalifate of 'Umar the Commander of the Faithful, and always regretted having failed to wait on his lordship the best of created beings. It is, however, related in the history of Ebn Hamdan that at the time when 'Umar bin al-Khattab marched to Aylay, Ka'bul-akhbar was dwelling in Syria, and that when the victorious banners of that Khalifah occupied the country, Ka'bul-akhbar made hast to wait on him, and to make his profession of the Faith. But Allah the Most High knows best.