Reflecting the consistent assertions made by Ethiopian Jews they dealt with or knew of, and after due investigation of their claims and their own Jewish behaviour, a number of Jewish legal authorities, in previous centuries and in modern times, have ruled "halakhically" (according to Jewish legal code) that the Beta Israel are indeed Jews, the descendants of the tribe of Dan, one of the Ten Lost Tribes. They believe that these people established a Jewish kingdom that lasted for hundreds of years. With the rise of Christianity and later Islam, schisms arose and three kingdoms competed. Eventually, the Christian and Muslim Ethiopian kingdoms reduced the Jewish kingdom to a small impoverished section. The earliest authority to rule this way was the 16th-century scholar David ibn Zimra (Radbaz), who explained elsewhere in a responsum concerning the status of a Beta Israel slave: