From
王维《送元二使安西》 (Wang Wei, Tang, 8th c., seeing off Yuan Er on a mission to Anxi in the Western Regions):
渭城朝雨浥轻尘,客舍青青柳色新。劝君更尽一杯酒,西出阳关无故人 (Morning rain in Weicheng has settled the light dust; the guesthouse willows are fresh and green again. Let me urge you to drink one more cup - once you pass west of Yang Pass there will be no old friends). Set to music as 《
阳关三叠》 (Yangguan Three Variations), it became the standard farewell song for over a thousand years.