《汉书·纪·成帝纪》
当春耕时，特令二千石劝勉农桑，要深入到农田上去，鼓励农民努力从事农业生产。
方东作时，其令二千石勉劝农桑，出入阡陌，致劳来之。
While spring plowing was in season, officials in charge of agriculture were specially ordered to encourage farming and sericulture. They were to go to the farms in person to encourage farmers to work hard at their agricultural production.