《旧唐书·列传·卷二十二》
内外的群官，由朝廷选任，从世族与平民中挑选，明镜般地考察他们，任职多年而有劳绩就提升官阶，考核政绩明确职务的升降。
内外群官，选自朝廷，擢士庶以任之，澄水镜以鉴之，年劳优其阶品，考绩明其黜陟。
The officials at home and abroad were selected by the court, chosen from among the gentry and commoners, examining them like a clear mirror, promoting them after many years of service and accomplishments, and assessing their political achievements to determine their promotion and demotion.