《史记·八书·封禅书》
为平乱伐叛等武事召集诸侯会兵三次，为政治、外交等文事集会了六次，前后九次集会诸侯，一统天下，诸侯无一人敢违背我。
兵车之会三，而乘车之会六，九合诸侯，一匡天下，诸侯莫违我。
When he dealt with rebellions and other martial matters, he summoned the feudal lords to gather their forces together three times; when he dealt with politics, diplomacy and other civil matters, he gathered them six times; in total, he summoned the feudal lords nine times, unified the whole country, and not one feudal lord dared disobey him.