1 Chronicles 25:9
Now the first lot came forth for Asaph to Joseph: the second to Gedaliah, who with his brethren and sons were twelve: (1 Chronicles 25:9)
For Asaph.
The order in which the names are listed suggests a definite method of distribution. An ingenious hypothesis has been worked out which assumes that there were three urns, one containing the names of the sons of Asaph, a second having the names of the sons of Jeduthun, and a third, the names of the sons of Heman. In addition to these (or instead of them), there could have been an urn with the names of the three main clans, to determine the order in which these would be chosen. The first lot fell to Asaph, and from there on each alternate name was one of the sons of Asaph till these were exhausted. The second lot fell to one of the sons of Jeduthun, and from here on each alternate name, with the exception of the sixth, was a son of Jeduthun until these were exhausted. After all the sons of Asaph had been taken, the names alternated between sons of Jeduthun and sons of Heman until the sons of Jeduthun had all been taken, which was with the 14th course. From the 15th course onward all the names are sons of Heman. Though the hypothesis sets forth a method that might have yielded the given results, there is no evidence that this was the method employed.