From
杜甫 曲江二首·其二 (Du Fu, Tang, 758):
酒债寻常行处有,
人生七十古来稀。
穿花蛱蝶深深见,
点水蜻蜓款款飞 (Wine debts are common wherever I go; a life of seventy has been rare since ancient times. Butterflies deep among the flowers come into view; dragonflies dot the water, gliding gently). This line gave Chinese the standard term
古稀 for 'seventy years old', still used at 70th-birthday celebrations today.